Disclaimer: This is only an estimation! Take the result with a grain of salt.
See this post about what dB is and how it affects FPV range.
This calculator assumes perfect conditions. There are many factors that can affect FPV range, so you are likely going to get less range in real life.
Frequency MHz
VTX Power dBm
VTX Antenna Gain dBi
VRX Antenna Gain dBi
VRX Sensitivity dBm
Link Margin dB
Other Losses dB
.
.
Distance Km
VTX Power mW to dB Look Up Table
mW dBm
1 0
10 10
25 13.98
50 16.99
100 20
200 23.01
300 24.77
400 26.02
500 26.99
600 27.78
800 29.03
1000 (1W) 30
1500 (1.5W) 31.76
2000 (2W) 33.01