dBm to Watts Converter
Convert RF power from dBm to watts and milliwatts. Enter dBm to get power in W, mW and dBW. Used in RF engineering, Wi-Fi, and telecommunications.
How to use this tool
- Enter power level in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your power and the full breakdown beneath it.
dBm is power expressed in decibels relative to 1 mW: P(W) = 10^(dBm/10) / 1000. This logarithmic scale is standard in RF engineering, telecommunications and Wi-Fi specifications. 0 dBm = 1 mW; every +10 dBm is a tenfold power increase.
Formula
P (W) = 10dBm / 10 / 1000
P (mW) = 10dBm / 10
P (dBW) = dBm − 30
How it works
dBm is a logarithmic power ratio referenced to 1 milliwatt, so converting to milliwatts requires raising 10 to the power of (dBm ÷ 10); dividing by 1000 gives watts.
The dBW figure follows directly because the reference shifts from 1 mW to 1 W — a factor of 1000 (30 dB) — so dBW is always exactly 30 less than dBm.
Worked example
Worked example — 0 dBm
- Input: 0 dBm.
- P (mW) = 10^(0/10) = 10^0 = 1.0 mW.
- P (W) = 1.0 / 1000 = 0.001 W.
- P (dBW) = 0 − 30 = −30 dBW.
1.0 mW, 0.001 W, −30 dBW.
Common mistakes to avoid
- Forgetting to divide by 1000 when converting mW to W — 0 dBm is 1 mW, not 1 W.
- Treating dBm as a linear value: doubling the dBm figure does not double the power; each +3 dBm doubles watts.
- Confusing dBm with dBW — dBW is always 30 less than dBm (e.g. 30 dBm = 0 dBW).
Key terms
- dBm
- Decibels relative to one milliwatt; a logarithmic unit used to express absolute RF power levels.
- dBW
- Decibels relative to one watt; 0 dBW equals 1 W, and dBW = dBm − 30.
- Logarithmic scale
- A scale where equal steps represent multiplication rather than addition, making it convenient for expressing the wide power ranges common in RF systems.
- Reference level
- The fixed power (1 mW for dBm, 1 W for dBW) against which a logarithmic ratio is measured.
- RF power
- Radio-frequency electrical power, typically measured in milliwatts or watts and often expressed in dBm in wireless engineering.
Frequently asked questions
- What is a typical Wi-Fi signal strength in dBm?
- -30 dBm is excellent (very close to the access point). -70 dBm is usable. Below -80 dBm connections become unreliable.
- What is the difference between dBm and dBW?
- Both are logarithmic power units. dBm references 1 mW; dBW references 1 W. dBW = dBm − 30. A 1 W transmitter is 30 dBm or 0 dBW.