dB / dBm / watt / volt converter
dBm = 10·log10(P ÷ 1 mW). Enter any one value in dBm, watts or volts (RMS, into 50 Ω) and read the other scales — including dBV / dBu references and the linear power ratio.
Value to convert
Conversions
dBm (ref 1 mW)
10·log10(P / 1 mW)
Watts
0.01 W
Voltage (50 Ω)
V = √(P × 50)
dBV reading
relative to 1 V RMS (dBV)
dB vs 0.775 V RMS (dBu)
0.775 V RMS (dBu)
Linear power ratio
10^(dBm/10), relative to 1 mW
About dB scales
A 3 dB change doubles or halves power; 10 dB is a factor of 10. dBm is always referenced to 1 mW, so 0 dBm = 1 mW, 10 dBm = 10 mW, 20 dBm = 100 mW, 30 dBm = 1 W. Voltage conversions assume a 50 Ω system (standard for RF) and an RMS measurement. Use the dBu reference when working against 600 Ω audio gear.
Building RF or audio? Find RF amplifiers and attenuators in our catalog.
Frequently asked questions
How do I convert dBm to watts?
dBm is power referenced to 1 mW: P = 10^(dBm/10) × 1 mW. So 0 dBm = 1 mW, 10 dBm = 10 mW, 20 dBm = 100 mW and 30 dBm = 1 W — the calculator shows watts, voltage and the linear ratio for any dBm input.
What is the difference between dBV and dBu?
dBV is referenced to 1 V RMS and dBu is referenced to 0.775 V RMS (the level that is 0 dBm into a 600 Ω line). Both appear in the results, and voltage conversions into watts assume a 50 Ω RF system and an RMS measurement.
How is voltage converted from dBm in a 50 Ω system?
The tool computes V = √(P × 50) from the power in watts. For example 10 dBm is 10 mW, which into 50 Ω is √(0.01 × 50) ≈ 0.707 V RMS; the corresponding dBV reading is 20 × log10(0.707) ≈ −3 dBV.
Voltage conversions assume a 50 Ω system and RMS readings. ICBOMS provides this tool for reference only.