dBm to Watts Converter
Convert a power in dBm to milliwatts, watts and dBW, with the RMS voltage it produces across a 50 Ω load.
Results
Power in watts
0.1
W
Power in milliwatts
100
mW
Power in dBW
-10.00
dBW
RMS voltage across 50 Ω
2.2361
V
What this tool does
dBm measures power in decibels relative to one milliwatt, so 0 dBm is 1 mW, every +10 dB multiplies by ten and every +3 dB roughly doubles: 20 dBm is 100 mW, 30 dBm is 1 W. Radio, Wi-Fi and fibre datasheets use it because powers span many orders of magnitude, from a +20 dBm router to a −90 dBm received signal — a factor of a billion billion. Adding dBm to dB of gain or loss gives the new level directly, which is the whole convenience.
Formula
P(mW) = 10^(dBm ÷ 10) · dBW = dBm − 30 · V = √(P × 50 Ω)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
db | Power in dBm | dBm |
W | Power in watts | W |
MW | Power in milliwatts | mW |
DW | Power in dBW | dBW |
V | RMS voltage across 50 Ω | V |
Worked example
- Power in dBm20 dBm
- Power in watts0.1 W
- Power in milliwatts100 mW
- Power in dBW-10.00 dBW
- RMS voltage across 50 Ω2.2361 V
Limitations
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.
- The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.