dBm to Watts Converter
Convert between dBm and watts for amateur radio power levels.
Includes common reference points and transmitter power chart.
Power Conversion
Power in radio systems is almost always expressed in dBm (decibels relative to 1 milliwatt) because the numbers span many orders of magnitude and gain/loss calculations become simple addition and subtraction.
Formulas:
- dBm to Watts: P(W) = 10^(dBm/10) / 1000
- Watts to dBm: dBm = 10 × log₁₀(P in milliwatts) = 10 × log₁₀(P_watts × 1000)
Key reference points:
- 0 dBm = 1 mW
- +10 dBm = 10 mW
- +20 dBm = 100 mW
- +30 dBm = 1 W
- +37 dBm = 5 W (handheld radio)
- +40 dBm = 10 W
- +47 dBm ≈ 50 W
- +50 dBm = 100 W (typical HF transceiver)
- +53 dBm ≈ 200 W
- +60 dBm = 1,000 W (1 kW amplifier)
- −100 dBm = 0.1 pW (weak signal reception)
- −120 dBm = 1 fW (typical receiver noise floor)
Why dBm is useful: A 100W transmitter (+50 dBm) loses 100 dB in free space, then gains 10 dBi from a directional antenna = −40 dBm received signal. Just add and subtract — no multiplication needed.
dBi vs dBd: Antenna gain in dBi is relative to an isotropic radiator. dBd is relative to a dipole. dBi = dBd + 2.15.