FPV Video Range Calculator

The Friis transmission equation

FPV range is governed by a 1946 RF formula that any physics student would recognize:

range = (c ÷ (4π × f)) × √(P_tx × G_tx × G_rx ÷ S_rx)

Translated to the working form most calculators use:

free-space path loss (dB) = 20 × log₁₀(distance_m) + 20 × log₁₀(frequency_MHz) + 32.45

The link budget is:

EIRP + receive antenna gain − receiver sensitivity = maximum allowable path loss

Solve for distance and you get a theoretical range. In open air with no obstacles and perfect antenna alignment, the formula is accurate within a few percent.

Why real range is always lower

Free-space assumes nothing absorbs or reflects the signal. The real world is full of trees (each costs 1 to 3 dB at 5.8 GHz), buildings (10+ dB through brick), water in the air (0.1 dB/km at 5.8 GHz, much more at 24 GHz), and reflected interference (multipath fading). Plan for 30 to 60% of the calculated theoretical range as your usable range, less in dense terrain.

Common FPV combinations

Antenna polarization matters

Linear-to-linear (dipole-to-dipole) antennas at perfect alignment work great. Mismatch the polarization by 90° and you lose 20 dB, about 90% of your range. Most FPV systems use circular polarization (RHCP or LHCP) on both ends, which trades 3 dB for orientation-independence. Mixing RHCP with LHCP is catastrophic; check both ends use the same handedness.

Local power limits

Most countries cap FPV transmit power: 25 mW for 5.8 GHz analog in the EU under EN 300 440 unrestricted, 200 mW in many countries with a HAM license, and up to 1000 mW in some jurisdictions. Always check your local rules before turning the dial up.