LEO Orbit Calculator

LEO Orbit Calculator: Calculate Orbital Period, Velocity, Coverage & Pass Duration

A LEO Orbit Calculator helps you estimate the key characteristics of a satellite operating in Low Earth Orbit (LEO). By entering the orbital altitude, you can calculate the satellite's orbital radius, orbital period, orbital velocity, number of orbits per day, maximum horizon slant range, ground footprint radius, and theoretical maximum overhead pass duration.

These calculations are useful for understanding how satellite altitude affects orbital mechanics and basic communication or coverage geometry. The calculator supports orbital altitudes from 160 km to 2,000 km and uses a simplified circular-orbit model based on Earth's equatorial radius and gravitational parameter.

For example, at an altitude of 550 km, the calculator estimates an orbital period of about 95.5 minutes, an orbital velocity of about 7.59 km/s, and roughly 15.1 revolutions per day.

Whether you're studying orbital mechanics, evaluating a conceptual satellite mission, planning a ground-station scenario, or simply trying to understand how LEO satellites work, this calculator provides a fast starting point.

What Is a LEO Orbit Calculator?

A LEO Orbit Calculator is a tool that estimates basic orbital and geometric parameters of a satellite in Low Earth Orbit from its altitude above Earth.

The orbital altitude is important because changing the altitude changes the satellite's distance from Earth's center. That change affects its orbital period and velocity, as well as how far toward the horizon the satellite can theoretically be seen.

This calculator takes one primary input:

Orbital altitude in kilometers (km)

It then calculates:

• Orbital altitude
• Orbital radius
• Orbital period
• Orbital velocity
• Orbits per day
• Maximum horizon slant range
• Ground footprint radius
• Maximum theoretical overhead pass duration
• A qualitative orbital-environment note related to atmospheric drag

The calculator accepts values from 160 km through 2,000 km.

It is designed for preliminary analysis rather than precise satellite mission planning. Real satellite operations require additional parameters such as orbital inclination, eccentricity, ground-station coordinates, minimum elevation angle, atmospheric conditions, and detailed orbit propagation.

What Is Low Earth Orbit (LEO)?

Low Earth Orbit, commonly abbreviated as LEO, refers to satellite orbits relatively close to Earth compared with higher orbital regimes such as Medium Earth Orbit (MEO) and Geostationary Earth Orbit (GEO).

LEO is widely used for applications including Earth observation, remote sensing, scientific missions, satellite communications, technology demonstrations, and human spaceflight.

One important characteristic of LEO is that satellites move around Earth at high orbital speeds. Because they are relatively close to Earth, they also experience atmospheric drag that can gradually reduce orbital energy. The importance of drag depends strongly on altitude and atmospheric conditions.

The calculator uses an Earth equatorial radius of:

6,378.137 km

The orbital radius is calculated by adding the altitude to this reference radius:

r = Rₑ + h

where:

• r = orbital radius
• Rₑ = Earth's equatorial radius
• h = orbital altitude

For example, if a satellite is at 550 km altitude:

r = 6,378.137 + 550

r = 6,928.137 km

That orbital radius is then used to calculate the satellite's orbital period, velocity, and other geometric parameters.

How Does the LEO Orbit Calculator Work?

The calculator follows a straightforward sequence of orbital-mechanics and geometric calculations.

Step 1: Enter Orbital Altitude

Enter the satellite's orbital altitude in kilometers.

The calculator accepts:

• Minimum: 160 km
• Maximum: 2,000 km
• Increment: 1 km
• Default example: 550 km

The altitude represents the satellite's height above the Earth's reference radius used in the calculation.

Step 2: Calculate Orbital Radius

The calculator adds the orbital altitude to Earth's equatorial radius:

r = Rₑ + h

The resulting orbital radius represents the satellite's approximate distance from the center of Earth.

Step 3: Calculate Orbital Period

The calculator uses the circular-orbit equation:

T = 2π√(r³/μ)

The result is initially calculated in seconds and then converted into minutes.

Step 4: Calculate Orbital Velocity

The circular orbital velocity is calculated using:

v = √(μ/r)

The output is displayed in kilometers per second.

Step 5: Calculate Orbits Per Day

The number of revolutions per day is calculated using:

Orbits per day = 86,400 / T

where 86,400 is the number of seconds in a day.

Step 6: Calculate Horizon Geometry

The calculator then estimates the satellite's maximum horizon slant range and the radius of its geometric ground footprint.

Step 7: Estimate Maximum Overhead Pass Duration

Finally, the calculator estimates the theoretical maximum duration of an overhead pass assuming a 0° elevation horizon.

How Is LEO Orbital Period Calculated?

The orbital period is the amount of time required for a satellite to complete one complete orbit around Earth.

For a simplified circular orbit, the calculator uses:

T = 2π√(r³/μ)

where:

• T = orbital period in seconds
• r = orbital radius in kilometers
• μ = Earth's gravitational parameter

The calculator uses:

μ = 398600.4418 km³/s²

The relationship between altitude and orbital period is important.

When altitude increases, the orbital radius increases. The larger orbital radius results in a longer orbital period.

In contrast, a lower circular orbit has a smaller orbital radius and therefore a shorter period.

The calculator converts the result from seconds to minutes so that the output is easier to interpret.

Why Is Orbital Period Important?

Orbital period is useful for understanding:

• How frequently a satellite circles Earth
• Approximate satellite timing
• Ground-station scheduling concepts
• Satellite tracking
• Earth-observation mission concepts
• Constellation analysis

However, orbital period should not be confused with revisit time for a particular location.

A satellite can complete an orbit around Earth without passing directly over a specific city or ground station. Revisit time depends on additional orbital parameters, including inclination and the satellite's ground track.

How Is LEO Orbital Velocity Calculated?

The orbital velocity represents the speed of a satellite traveling along its circular orbit.

The calculator uses:

v = √(μ/r)

where:

• v = orbital velocity in km/s
• μ = Earth's gravitational parameter
• r = orbital radius

An important orbital-mechanics relationship is that circular orbital velocity decreases as orbital radius increases.

That means a satellite in a lower circular orbit generally travels faster than one in a higher circular orbit.

This can seem counterintuitive because higher-altitude satellites have farther to travel around Earth. However, the gravitational acceleration is weaker at greater distances, so the circular velocity required for the higher orbit is lower.

The calculator displays orbital velocity in km/s, making it particularly useful for aerospace, satellite, and orbital-mechanics calculations.

What Does Orbits Per Day Mean?

The orbits per day value indicates approximately how many complete revolutions the satellite makes around Earth during a 24-hour period.

The calculator uses:

Orbits per day = 86,400 / orbital period in seconds

For example, if a satellite has an orbital period of approximately 95.5 minutes, it completes roughly 15 revolutions per day.

As altitude increases, the orbital period increases, so the number of revolutions per day generally decreases.

Why Does This Matter?

The value can help you develop an initial understanding of:

• Satellite movement
• Observation opportunities
• Ground-station scheduling
• Tracking frequency
• Orbital repetition
• Constellation behavior

One important distinction is that orbits per day does not mean passes over a particular ground station per day.

A satellite's actual visibility over a particular location depends on the orbit's inclination, ground track, observer location, elevation mask, and Earth rotation.

What Is Maximum Horizon Slant Range?

The maximum horizon slant range represents the straight-line distance between the satellite and a point on Earth's surface when the satellite is at the geometric horizon.

The calculator uses:

dₛₗₐₙₜ = √(r² − Rₑ²)

where:

• dₛₗₐₙₜ = maximum horizon slant range
• r = orbital radius
• Rₑ = Earth's radius

This geometry assumes a 0° elevation angle, meaning the satellite is exactly at the theoretical horizon.

What Is Slant Range?

Slant range is the direct, straight-line distance between a ground location and the satellite.

It is different from ground distance.

For example, a satellite may be thousands of kilometers away in a straight line while the corresponding surface distance between the observer and the satellite's sub-satellite point is a different value.

Why Is Horizon Slant Range Useful?

It can provide useful geometric context for:

• Satellite communication
• Ground-station planning
• Antenna tracking
• RF propagation analysis
• Satellite visibility studies

However, the result should not be interpreted as the maximum practical communication range. A communication link also depends on transmitter power, antenna gain, receiver sensitivity, frequency, atmospheric losses, noise, and other link-budget parameters.

What Is a LEO Satellite Ground Footprint?

A satellite's ground footprint describes the region on Earth's surface that is geometrically visible from the satellite under a particular visibility assumption.

The LEO Orbit Calculator estimates a theoretical footprint radius using the central angle between the satellite's sub-satellite point and the horizon.

First, it calculates the central angle:

γ = acos(Rₑ/r)

Then it calculates the surface distance:

Ground Footprint Radius = Rₑ × γ

Here, the angle is expressed in radians when used in the distance calculation.

Ground Footprint vs Slant Range

These two outputs represent different measurements.

This distinction is important when interpreting satellite coverage.

Does Footprint Mean Actual Communication Coverage?

Not necessarily.

The calculator provides a geometric footprint estimate. Real communication coverage can be significantly different.

Practical coverage can be affected by:

• Antenna beamwidth
• Minimum elevation angle
• Transmitter power
• Receiver sensitivity
• Frequency
• Antenna gain
• Terrain
• Atmospheric effects
• Polarization
• Link-budget limitations

Therefore, the footprint result is best treated as a geometric starting point rather than a guaranteed service area.

How Long Can a LEO Satellite Be Visible?

A satellite pass is the period during which a satellite remains above a specified elevation threshold for an observer.

The calculator estimates the maximum theoretical overhead pass duration.

Its formula is:

Maximum Pass Duration = (Period × γ) / π

The calculation assumes an overhead or zenith pass and a 0° elevation mask.

This represents an idealized maximum visibility duration under the calculator's geometry.

An overhead pass is important because it represents the geometry that can produce the longest horizon-to-horizon passage for a given orbit under these assumptions.

Actual visibility from a particular ground station can be shorter.

What Determines Actual Pass Duration?

Real pass duration depends on:

• Ground-station latitude
• Ground-station longitude
• Satellite inclination
• Orbital geometry
• Ground track
• Minimum elevation angle
• Earth rotation
• Atmospheric effects
• Tracking constraints

Therefore, this calculator should not be used as an exact satellite pass-prediction system.

For exact pass times, you need a satellite orbit model and observer coordinates.

How Does Atmospheric Drag Affect LEO Satellites?

Atmospheric drag is an important consideration in LEO because Earth's upper atmosphere extends well above the surface.

Even though the atmosphere is extremely thin at typical LEO altitudes, its density can still affect satellites. Drag removes orbital energy and can contribute to orbital decay.

The calculator provides a qualitative Orbital Environment Note based on altitude.

Below 350 km

The calculator classifies the environment as:

High atmospheric drag — rapid orbital decay

350–700 km

The calculator classifies the environment as:

Moderate drag — station-keeping required

Above 700 km

The calculator classifies the environment as:

Low atmospheric drag — stable orbit

These categories should be understood as simplified calculator guidance, not universal engineering classifications.

Actual atmospheric drag can vary substantially depending on:

• Solar activity
• Atmospheric density
• Satellite cross-sectional area
• Satellite mass
• Attitude
• Space weather
• Orbital altitude

A detailed orbital-decay calculation requires a more sophisticated atmospheric-density and drag model.

Real-Life Example: A 550 km LEO Satellite

Consider a hypothetical Earth-observation company evaluating a conceptual satellite orbit at 550 km altitude.

The team wants to quickly understand the basic orbital characteristics before moving to more detailed mission analysis.

Enter:

Orbital Altitude = 550 km

Using the calculator's equations and constants, the approximate results are:

These numbers provide a useful first-order picture of the orbit.

The satellite completes approximately 15 revolutions around Earth each day. Its circular orbital velocity is approximately 7.59 km/s, and its orbital period is roughly 95.5 minutes.

The calculated footprint radius is approximately 2,558 km, but this should not be interpreted as a guaranteed communication or imaging area. It represents the geometric surface distance to the horizon under the calculator's assumptions.

Similarly, the approximately 25.3-minute pass duration represents a theoretical maximum overhead pass with a 0° elevation mask. A real ground station may experience a shorter useful pass because it may require a higher minimum elevation angle.

This example demonstrates how a single altitude input can provide several useful insights into a conceptual LEO mission.

Real-World Uses of a LEO Orbit Calculator

1. Satellite Communication

Satellite communication engineers can use basic orbital calculations to understand how altitude affects:

• Orbital timing
• Visibility geometry
• Ground footprint
• Potential ground-station contact windows

The calculator is particularly useful during early-stage analysis before detailed RF and orbital simulations.

A complete communication-system design still requires a link budget, antenna characteristics, frequency, transmit power, receiver sensitivity, propagation losses, and other parameters.

2. Earth Observation

LEO is widely used for Earth-observation missions because satellites can operate relatively close to Earth's surface.

The calculator can help users understand:

• Orbital period
• Number of revolutions per day
• Geometric footprint
• Approximate visibility duration

However, actual imaging coverage depends on factors such as sensor field of view, swath width, orbital inclination, satellite attitude, and ground-track geometry.

3. Amateur Radio Satellite Operations

Amateur radio operators interested in satellite communications can use the calculator to build intuition about LEO orbital behavior.

The outputs can help explain:

• How quickly satellites move
• Why passes are time-limited
• How altitude affects visibility
• Why satellite tracking is necessary

For an actual radio pass, however, a dedicated pass-prediction system is needed.

4. Aerospace Education

The calculator is useful as an educational tool for students studying:

• Orbital mechanics
• Physics
• Aerospace engineering
• Satellite communications
• Astronomy
• RF engineering

Instead of working through every equation manually, students can change altitude and observe how the outputs respond.

For example, increasing altitude should generally produce:

• Longer orbital periods
• Lower circular orbital velocity
• Fewer revolutions per day
• Greater geometric horizon range
• Larger geometric footprint

5. Preliminary Mission Design

During the conceptual phase of a satellite project, engineers may need quick estimates before running detailed simulations.

The calculator can provide an initial reference for:

• Candidate altitudes
• Orbital timing
• Velocity
• Coverage geometry
• Drag context

It should be considered a preliminary analytical tool, not a replacement for professional mission-analysis software.

How to Use the LEO Orbit Calculator

Using the calculator requires only one input.

Step 1: Enter the Orbital Altitude

Enter the satellite altitude in kilometers.

For example:

550 km

Step 2: Check the Valid Range

The calculator accepts values between:

160 km and 2,000 km

Step 3: Calculate

The tool automatically calculates the orbital and geometric parameters.

Step 4: Review the Results

You'll receive:

1. Orbital altitude
2. Orbital radius
3. Orbital period
4. Orbital velocity
5. Orbits per day
6. Maximum horizon slant range
7. Ground footprint radius
8. Maximum overhead pass duration
9. Orbital environment note

Step 5: Compare Different Altitudes

For better insight, try several altitudes instead of analyzing only one.

For example, compare:

• 300 km
• 500 km
• 550 km
• 700 km
• 1,000 km
• 1,500 km

This makes the relationship between altitude and orbital characteristics much easier to understand.

LEO Orbit Calculator Formulas

The calculator uses several standard relationships for simplified circular-orbit and Earth-geometry calculations.

Orbital Radius

r = Rₑ + h

Where:

• r = orbital radius in km
• Rₑ = Earth's equatorial radius
• h = orbital altitude

The calculator uses:

Rₑ = 6,378.137 km

Orbital Period

T = 2π√(r³/μ)

Where:

• T = orbital period in seconds
• r = orbital radius
• μ = Earth's gravitational parameter

The calculator uses:

μ = 398600.4418 km³/s²

Orbital Velocity

v = √(μ/r)

Where:

• v = circular orbital velocity in km/s
• μ = Earth's gravitational parameter
• r = orbital radius

Orbits Per Day

N = 86,400/T

Where:

• N = revolutions per day
• T = orbital period in seconds

Maximum Horizon Slant Range

d = √(r² − Rₑ²)

This calculates the geometric straight-line distance between the satellite and the horizon point.

Horizon Central Angle

γ = acos(Rₑ/r)

The central angle is measured from Earth's center between the sub-satellite point and the horizon point.

Ground Footprint Radius

D = Rₑ × γ

This converts the central angle into an approximate distance along Earth's surface.

Maximum Overhead Pass Duration

t = (T × γ) / π

This estimates the theoretical maximum overhead pass duration under the calculator's idealized 0° elevation assumption.

How Altitude Changes LEO Satellite Performance

Altitude is one of the most influential variables in these calculations.

Consider what happens as the altitude increases.

Orbital Radius Increases

Because:

r = Rₑ + h

a higher altitude produces a larger orbital radius.

Orbital Period Increases

The orbital period depends on the cube of orbital radius inside the square-root relationship:

T ∝ r³ᐟ²

Therefore, higher circular orbits take longer to complete.

Orbital Velocity Decreases

Because:

v ∝ 1/√r

the circular orbital velocity decreases as orbital radius increases.

Orbits Per Day Decrease

A longer orbital period means fewer complete revolutions in 24 hours.

Geometric Footprint Increases

A satellite farther from Earth can theoretically see farther toward the horizon, increasing its geometric footprint.

Atmospheric Drag Generally Decreases

As altitude increases, atmospheric density generally decreases, reducing the influence of atmospheric drag compared with lower LEO altitudes.

This creates an important engineering tradeoff.

Lower altitude:

• Higher circular velocity
• Shorter orbital period
• More revolutions per day
• Smaller geometric footprint
• Greater atmospheric-drag concerns

Higher altitude:

• Lower circular velocity
• Longer orbital period
• Fewer revolutions per day
• Larger geometric footprint
• Generally lower atmospheric-drag influence

There is no universally "best" LEO altitude. The appropriate altitude depends on the mission's objectives and constraints.

Limitations and Assumptions of the LEO Orbit Calculator

The LEO Orbit Calculator is intentionally simplified.

It assumes an idealized circular orbit and uses fixed Earth constants. This makes the calculations fast and reproducible but means the results should not be treated as exact mission predictions.

Major assumptions include:

• Circular orbit
• Two-body gravitational model
• Fixed Earth equatorial radius
• Fixed gravitational parameter
• Idealized horizon geometry
• 0° elevation horizon
• Overhead pass for the maximum pass-duration estimate
• No detailed atmospheric model
• No orbital eccentricity
• No inclination-specific calculations
• No ground-station coordinates

The calculator does not directly calculate:

• Exact satellite position
• TLE propagation
• Specific satellite pass times
• Doppler shift
• RF link budget
• Antenna pointing angles
• Exact revisit time
• Eclipse duration
• Detailed orbital decay
• Constellation coverage

These limitations are important because satellite operations are highly dependent on orbital geometry and environmental conditions.

For example, knowing that a satellite completes 15 orbits per day does not tell you that a particular city will see 15 passes per day.

Likewise, knowing the geometric footprint radius does not mean that a communication system can provide service throughout that entire area.

LEO Orbit Calculator vs Detailed Satellite Orbit Analysis

A simple LEO calculator and professional satellite-analysis software serve different purposes.

LEO Orbit Calculator

Best suited for:

• Quick calculations
• Education
• Preliminary analysis
• Concept development
• Understanding orbital relationships
• Comparing candidate altitudes

Detailed Orbital Analysis

Professional mission analysis can require:

• Numerical orbit propagation
• TLE or state-vector data
• Orbital eccentricity
• Inclination
• Earth's nonspherical gravity
• Atmospheric drag models
• Solar and lunar perturbations
• Ground-station coordinates
• Time-dependent calculations
• Space-weather information

Therefore, the LEO Orbit Calculator should be viewed as a first-pass analytical tool.

It provides the fundamental relationships needed to understand how altitude affects orbital behavior, but it does not replace detailed mission-analysis software.

Frequently Asked Questions

What is a LEO Orbit Calculator?

A LEO Orbit Calculator estimates basic characteristics of a Low Earth Orbit satellite from its orbital altitude. This calculator provides orbital period, velocity, revolutions per day, horizon slant range, ground footprint radius, and maximum theoretical overhead pass duration.

How do you calculate the orbital period of a LEO satellite?

For an idealized circular orbit, orbital period can be calculated using:

T = 2π√(r³/μ)

where r is orbital radius and μ is Earth's gravitational parameter.

What is the orbital velocity of a LEO satellite?

For a simplified circular orbit, orbital velocity is calculated using:

v = √(μ/r)

The exact velocity depends on the satellite's orbital radius and, for non-circular orbits, its position along the orbit.

How many times does a LEO satellite orbit Earth per day?

The number depends on altitude. The LEO Orbit Calculator calculates it by dividing 86,400 seconds by the satellite's orbital period in seconds.

A satellite at approximately 550 km altitude has an idealized orbital period of about 95.5 minutes, corresponding to roughly 15.1 revolutions per day.

What is a LEO satellite footprint?

A LEO satellite footprint is the region of Earth's surface that is geometrically visible from the satellite under a specified visibility assumption. This calculator estimates the footprint radius using the horizon geometry and Earth's reference radius.

How far can a LEO satellite see?

The theoretical distance to the horizon depends on orbital altitude. The calculator estimates this using:

d = √(r² − Rₑ²)

This is a geometric slant-range calculation and should not be confused with practical RF communication range.

How long does a LEO satellite pass last?

Pass duration depends on the satellite's orbit and the observer's location. This calculator estimates the maximum theoretical overhead pass duration under a 0° elevation assumption. Actual ground-station passes can be shorter.

Does higher altitude increase LEO coverage?

Higher altitude generally increases the satellite's geometric horizon and therefore its theoretical surface footprint. However, practical communication coverage depends on antenna patterns, link budgets, elevation masks, terrain, and other system constraints.

Does atmospheric drag affect LEO satellites?

Yes. Atmospheric drag can remove orbital energy and contribute to orbital decay. Its significance depends on altitude and changing atmospheric conditions, including solar activity.

Is this LEO calculator accurate enough for real satellite missions?

It is suitable for preliminary calculations and educational purposes. It is not a replacement for detailed orbital propagation, mission analysis, atmospheric modeling, or RF link-budget calculations.

Practical Tips for Using LEO Orbit Results

To get more value from the calculator:

1. Check your units. The altitude input is in kilometers.
2. Compare multiple altitudes. A single altitude does not show the full relationship between orbital parameters.
3. Use orbital period to understand timing.
4. Use orbital velocity to understand satellite motion.
5. Use footprint radius as a geometric estimate, not guaranteed RF coverage.
6. Treat horizon slant range as a line-of-sight geometry calculation.
7. Don't interpret maximum pass duration as an exact ground-station contact time.
8. Use detailed propagation tools for actual satellite tracking.
9. Consider atmospheric drag when evaluating lower LEO altitudes.
10. Combine orbital calculations with link-budget analysis for communication-system design.

Conclusion

The LEO Orbit Calculator provides a convenient way to understand how orbital altitude influences the fundamental characteristics of a Low Earth Orbit satellite.

By entering a single altitude value, you can estimate the satellite's orbital radius, orbital period, orbital velocity, revolutions per day, maximum horizon slant range, ground footprint radius, and theoretical maximum overhead pass duration.

The calculator also provides a qualitative atmospheric-drag assessment, helping users understand why very low LEO altitudes can experience significantly greater drag-related challenges.

A 550 km example demonstrates how these calculations come together: an idealized satellite at this altitude has an orbital period of approximately 95.5 minutes, travels at about 7.59 km/s, and completes roughly 15.1 revolutions per day.

The key is to understand what these numbers represent. They are valuable first-order estimates based on simplified circular-orbit and geometric assumptions. Actual satellite operations require additional information such as orbital inclination, eccentricity, observer coordinates, elevation constraints, atmospheric conditions, and detailed RF or orbital models.

For students, engineers, satellite enthusiasts, and early-stage mission planners, the calculator provides a fast way to connect orbital altitude with satellite speed, timing, visibility, and coverage geometry.

Enter your orbital altitude into the LEO Orbit Calculator and explore how changing altitude changes the behavior of a Low Earth Orbit satellite.