Radio Link Budget Calculator
The radio link budget calculator determines whether a wireless communication link will work by accounting for all gains and losses in the signal path. Starting from the transmit power and adding antenna gains, then subtracting free space path loss, cable losses, and other impairments, the calculator arrives at the received signal level. Comparing this to the receiver sensitivity gives the link margin - how much safety margin exists above the minimum workable signal. Link budget calculations are essential for cellular network design, satellite uplinks, Wi-Fi coverage planning, IoT deployments, and any scenario where a reliable wireless connection is needed over a specific range.
Link budget formula
FSPL(dB) = 20*log10(d_km) + 20*log10(f_GHz) + 92.44
EIRP = P_tx + G_tx - L_tx
RSL = EIRP - FSPL + G_rx - L_rx
Link margin = RSL - Receiver sensitivity
Understanding link margin
- Margin < 0 dB: link will fail under normal conditions.
- 0 to 5 dB: marginal, will fail in rain or heavy foliage.
- 5 to 10 dB: adequate for short-range indoor links.
- 10 to 20 dB: good margin for outdoor point-to-point links.
- Above 20 dB: robust, tolerant of significant interference and fading.
Link budget: frequently asked questions
What is a link budget?
A link budget is an accounting of all the gains and losses in a radio transmission path from transmitter to receiver. It includes transmit power, antenna gains, cable losses, free space path loss, and receiver sensitivity to determine whether the received signal will be strong enough for reliable communication.
What is free space path loss?
Free space path loss (FSPL) is the attenuation of radio waves travelling through free space with no obstacles. FSPL(dB) = 20*log10(d) + 20*log10(f) + 20*log10(4*pi/c), where d is distance in meters and f is frequency in Hz. It increases by 6 dB every time distance doubles and by 6 dB for each octave increase in frequency.
What is link margin?
Link margin is the difference between the received signal level and the minimum receiver sensitivity required for reliable operation. A positive margin means the link will work; a margin above 10 dB is considered robust. Zero or negative margin means the link will fail or be unreliable.
What is receiver sensitivity?
Receiver sensitivity is the minimum signal power the receiver can detect and decode reliably. It is determined by the thermal noise floor, receiver noise figure, required SNR for the modulation scheme, and bandwidth. A typical Wi-Fi receiver has sensitivity around -90 to -95 dBm.
How do I improve a marginal link budget?
Increase transmit power (subject to regulatory limits), use higher-gain antennas, reduce cable losses, lower the receiver noise figure, choose a modulation scheme with lower SNR requirements, reduce distance, or add a repeater. The link budget shows exactly where the budget is being spent.
Official sources
- ITU-R: ITU-R P.525 - Calculation of free-space attenuation.
- FCC: FCC Engineering and Technology Division.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.