Watts to dBm Calculator
Convert between watts and dBm for radio, WiFi, cellular, and satellite power calculations. Enter watts to get dBm, or switch the direction to convert dBm to watts. The tool also shows milliwatts and dBW for quick cross-reference.
dBm (decibel-milliwatts) is a logarithmic unit of power relative to one milliwatt. It is the standard unit used in RF engineering, wireless networking, and radio broadcasting because it turns wide power ranges into manageable numbers and multiplication into addition.
Watts to dBm formula:
dBm = 10 × log10(P × 1000), where P is power in watts.
An equivalent form is dBm = 30 + 10 × log10(W), which is the version most often seen in a watts to dbm formula excel sheet: the cell formula is usually "=30+10*LOG10(A1)".
dBm to watts formula:
Watts = 10^((dBm − 30) / 10)
Common watts to dBm reference
| Watts | dBm | Context |
|---|---|---|
| 0.001 W (1 mW) | 0 dBm | Bluetooth Class 3 |
| 0.01 W | 10 dBm | Low-power WiFi |
| 0.1 W | 20 dBm | WiFi client TX (100 mW) |
| 1 W | 30 dBm | Max FCC WiFi EIRP (point-to-multi) |
| 5 W | 36.9897 dBm | Ham radio handheld |
| 10 W | 40 dBm | Ham radio mobile (low) |
| 25 W | 43.9794 dBm | Public safety radio |
| 50 W | 46.9897 dBm | Mobile ham / amateur HF |
| 100 W | 50 dBm | Amateur HF transceiver |
| 1,000 W | 60 dBm | AM radio low-power |
This dBm to watts table uses the exact formula dBm = 30 + 10 × log10(W), rounded to four decimal places. Every 3 dB step is a power doubling, every 10 dB step is a 10× power increase.
Why engineers use dBm
Adding dB values is easier than multiplying linear power. If an amplifier has 20 dB gain and the input is 10 dBm, the output is 30 dBm. No multiplication required. Path loss, antenna gain, and receiver sensitivity are all expressed in dB or dBm for the same reason.
Quick mental shortcuts
- +3 dB = double the watts
- +10 dB = 10× the watts
- +20 dB = 100× the watts
- −3 dB = half the watts