dBm to watts calculator
Convert any power or voltage level to every other one across a 50, 75 or 600 Ω load, or turn a dB figure into power and voltage ratios.
- Power level
- 10 dBm
- Power level
- -20 dBW
- Voltage across 50 Ω
- 707.1 mVrms
- Voltage, sine
- 2 Vpp
- Voltage level
- 117 dBµV
- Voltage level
- -3.01 dBV
- Voltage level
- -0.7963 dBu Referred to 0.775 V.
| dBm | Power | Vrms | dBµV |
|---|---|---|---|
| -60 | 1 nW | 224 µV | 46.99 |
| -50 | 10 nW | 707 µV | 56.99 |
| -40 | 100 nW | 2.24 mV | 66.99 |
| -30 | 1 µW | 7.07 mV | 76.99 |
| -20 | 10 µW | 22.4 mV | 86.99 |
| -10 | 100 µW | 70.7 mV | 96.99 |
| 0 | 1 mW | 224 mV | 107 |
| +10 | 10 mW | 707 mV | 117 |
| +20 | 100 mW | 2.24 V | 127 |
| +30 | 1 W | 7.07 V | 137 |
| +40 | 10 W | 22.4 V | 147 |
| +50 | 100 W | 70.7 V | 157 |
| +60 | 1 kW | 224 V | 167 |
How this is calculated
dBm = 10 · lg( P / 1 mW ) dBW = 10 · lg( P / 1 W ) Vrms = sqrt( P · R ) Vpp = 2 · sqrt(2) · Vrms (sine) dBµV = 20 · lg( Vrms / 1 µV ) dBV = 20 · lg( Vrms / 1 V ) dBu = 20 · lg( Vrms / 0.775 V ) Power ratio = 10^(dB / 10) Voltage ratio = 10^(dB / 20)
- Load
- Voltage figures assume a purely resistive load of the chosen value. 0 dBm is 0.2236 Vrms in 50 Ω and 0.7746 Vrms in 600 Ω.
- dBu
- Referred to 0.775 V r.m.s., rounded from the 0.7746 V that dissipates 1 mW in 600 Ω, so in 600 Ω dBu and dBm agree within 0.005 dB. In any other load, dBu ≈ dBm + 10 · lg(R / 600).
- Vpp
- Peak to peak assumes a sine wave. Other waveforms have a different crest factor.
- Ratios
- A voltage ratio in dB uses 20 · lg. It matches the power ratio only when both voltages are across equal impedances.
- Recommendation ITU-R V.574-5, Use of the decibel and the neper in telecommunications08/2015, sections 1, 6.1, 6.5 and 8
Questions
30 dBm is 1 W. Every 10 dB is a factor of 10 in power, so 20 dBm is 100 mW, 40 dBm is 10 W and 0 dBm is 1 mW.
It depends on the load. 0 dBm is 0.2236 Vrms in 50 Ω, 0.2739 Vrms in 75 Ω and 0.7746 Vrms in 600 Ω. Pick the load before reading a voltage off a dBm figure.
In 50 Ω, add 107 dB: 0 dBm is 107.0 dBµV. In 75 Ω the offset is 108.8 dB. The offset changes with the load because it passes through a voltage.
Power ratios use 10 · lg and voltage ratios use 20 · lg, because power goes with voltage squared. 3.01 dB is a power ratio of 2; 6.02 dB is a voltage ratio of 2, which is a power ratio of 4 across the same impedance.