What this converter does
This converter turns power in watts into a dBm level and back. The dBm scale is logarithmic, so a power ratio becomes a sum of decibels — every ten-times change in watts is +10 dB. Type a wattage and read the dBm level instantly.
Because dBm references one milliwatt, 1 W is 30 dBm and 1 mW is 0 dBm. It is the standard unit for RF transmit power and link budgets in wireless and networking.
The units it covers
These are two ways to state the same RF power — a logarithmic level (dBm) and linear power (watts), tied by a base-10 relationship.
View all units & their values
| Unit | Symbol | Value | Mainly used |
|---|---|---|---|
| Decibel-milliwatt | dBm | log | RF & signal power level |
| Watt | W | linear | Actual power |
| Milliwatt | mW | linear | dBm reference (0 dBm = 1 mW) |
The formula
dBm is ten times the base-10 log of power in milliwatts, so the link to watts is exponential, not a fixed factor:
W = 10^((dBm − 30) ÷ 10)Where:
- dBm = power level referenced to 1 milliwatt
- W = power in watts
- 30 = the mW→W offset (0 dBm = 1 mW = 0.001 W)
Worked example
Convert 100 W to dBm.
dBm = 10 × log₁₀(W) + 3010 × log₁₀(100) + 30 = 50 dBmSo 100 W is 50 dBm.
The units in this example
Linear power. One watt equals 30 dBm; a milliwatt equals 0 dBm.
- 1 W = 30 dBm
- 0.001 W = 0 dBm
- 100 W = 50 dBm
- 0.5 W ≈ 27 dBm
A logarithmic power level referenced to 1 mW, used for RF power and sensitivity.
- 0 dBm = 1 mW
- 30 dBm = 1 W
- +3 dBm ≈ ×2 power
- +10 dBm = ×10 power