dBm to Watts Converter (and Watts to dBm)
By Santaji GadepatilinUpdated October 28, 2026
dBm expresses power in decibels relative to 1 milliwatt, so RF and optical power levels spanning many orders of magnitude become easy numbers to add and subtract. This dBm to watts converter works both ways and shows the equivalent voltage in a 50 Ω system — see decibels in electronics: dB and dBm.
How to use the dBm to watts converter
Enter a value in dBm to get watts (choose W, mW or kW), dBW and the RMS voltage across a 50 Ω load. To convert from watts, enter the power and press × on dBm.
dBm to watts formula
P(mW) = 10dBm/10 · dBm = 10 log₁₀(P/1 mW) · dBW = dBm − 30
dBm to watts table
| dBm | Power | Voltage (50 Ω) |
|---|---|---|
| -90 | 1e-06 µW | 7.07e-06 V |
| -60 | 0.001 µW | 0.000224 V |
| -30 | 1 µW | 0.00707 V |
| -10 | 100 µW | 0.0707 V |
| 0 | 1 mW | 0.224 V |
| 10 | 10 mW | 0.707 V |
| 20 | 100 mW | 2.24 V |
| 27 | 501.187 mW | 5.01 V |
| 30 | 1 W | 7.07 V |
| 40 | 10 W | 22.4 V |
| 50 | 100 W | 70.7 V |
| 60 | 1000 W | 224 V |
Typical power levels
| Signal | Level |
|---|---|
| Wi-Fi router transmit | 15–20 dBm |
| Mobile phone transmit (max) | 23–33 dBm |
| Wi-Fi receive (good) | −30 to −60 dBm |
| Wi-Fi receive (usable limit) | about −80 dBm |
| GPS signal at ground | about −130 dBm |
| Fibre optic transmitter | −10 to +3 dBm |
Link budgets
In dB terms, you simply add gains and subtract losses: transmit 20 dBm + 6 dBi antenna − 80 dB path loss + 3 dBi antenna = −51 dBm received.
Frequently asked questions
How do I convert dBm to watts?
P(W) = 10^(dBm/10) ÷ 1,000. 20 dBm = 100 mW; 30 dBm = 1 W.
How do I convert watts to dBm?
dBm = 10 × log₁₀(P in mW). 1 W = 30 dBm; 10 W = 40 dBm.
What is the difference between dBm and dBW?
dBW is referenced to 1 W, so dBW = dBm − 30.
What do negative dBm values mean?
Power below 1 mW. Wi-Fi signals of −30 to −70 dBm are tiny fractions of a milliwatt.