Friis Transmission Equation Calculator
Calculate free-space path loss, EIRP, and received power using the Friis transmission equation.
6
Inputs
Live
Math
3
Related
Enter parameters and click Calculate to view results
Formula & Theory
Pr = Pt + Gt + Gr - FSPL - System LossThis formula is used to calculate antenna parameters for friis transmission equation calculator.
Overview
Friis Transmission Equation helps you calculate design values for a link budget & rf project from Frequency, Distance, Transmit Power, Transmit Antenna Gain, Receive Antenna Gain, System Loss. Calculate free-space path loss, EIRP, and received power using the Friis transmission equation. Use the result to make an informed first design decision before choosing hardware, setting dimensions, or evaluating the RF system in its final environment.
Input Guide
Enter Frequency, Distance, Transmit Power, Transmit Antenna Gain, Receive Antenna Gain, System Loss exactly in the units shown by this friis transmission equation. Check the operating band, unit prefix, and decimal position before calculating; these are the inputs used by the formula.
- Frequency — use MHz.
- Distance — use km.
- Transmit Power — use dBm.
- Transmit Antenna Gain — use dBi.
- Receive Antenna Gain — use dBi.
- System Loss — use dB.
Output Guide
The results describe the calculated friis transmission equation values for the inputs you entered. Check each value against the available space, selected components, feed system, and operating conditions before making a final design decision.
How This Calculator Works
The Friis Transmission Equation uses Pr = Pt + Gt + Gr - FSPL - System Loss. Supply Frequency (MHz), Distance (km), Transmit Power (dBm), Transmit Antenna Gain (dBi), Receive Antenna Gain (dBi), System Loss (dB) in the displayed units, then use the calculated values as the first engineering target for this link budget & rf design or analysis.
Design Notes
This link budget & rf calculation is based on Pr = Pt + Gt + Gr - FSPL - System Loss. Real-world accuracy depends on factors such as material properties, losses, mounting, nearby conductors, ground interaction, feed-line effects, and construction tolerance. Confirm the final system with measurement or simulation.
Build and Tuning Notes
Apply the friis transmission equation result as an initial target, then validate it in the intended installation. Keep the physical layout and feed arrangement consistent while testing, change one parameter at a time, and record the measured outcome before making another adjustment.
Frequently Asked Questions
What does the Friis Transmission Equation calculate?
Calculate free-space path loss, EIRP, and received power using the Friis transmission equation. The calculation provides an initial design value based on Frequency (MHz), Distance (km), Transmit Power (dBm), Transmit Antenna Gain (dBi), Receive Antenna Gain (dBi), System Loss (dB).
Which inputs are needed for the Friis Transmission Equation?
Enter Frequency (MHz), Distance (km), Transmit Power (dBm), Transmit Antenna Gain (dBi), Receive Antenna Gain (dBi), System Loss (dB) using the displayed units. Each value directly affects the calculated result, so confirm the unit and operating conditions before running the calculation.
How accurate is this friis transmission equation?
It follows Pr = Pt + Gt + Gr - FSPL - System Loss. It is accurate for the formula assumptions, but installed performance can change because of materials, loss, environment, mounting, nearby objects, and measurement uncertainty.
What should I do after using the Friis Transmission Equation?
Compare the result with the practical constraints of your link budget & rf system, then validate the completed design with appropriate measurement equipment or simulation.
Alex Warren
B.Sc. in Electrical & Electronic Engineering (EEE)
Alex specialises in antenna design and wave propagation. His expertise helps ensure these calculators present practical RF concepts, useful design estimates, and clear engineering guidance for students, HAM operators, and wireless professionals.