dB / dBm / dBV Converter
Convert dB, dBm, dBV, watts, volts, voltage gain and power gain for RF, audio, electronics and signal-level calculations.
📡 Quick Rule: dBm is an absolute power level referenced to 1mW. dBV is an absolute voltage level referenced to 1V RMS. Plain dB is only a ratio. Use this with the PCB Trace Impedance Calculator, Op-Amp Calculator, Power Dissipation Calculator, Reactance Calculator and RC Time Constant Calculator.
📡 dB Ratio vs dBm Power vs dBV Voltage
Input Mode
dBm Value
Power Value
System Impedance
dBm is referenced to 1 milliwatt. In a 50Ω RF system, dBm can also be converted to RMS voltage using V = √(P × R). Use Ω, kΩ or MΩ for impedance when converting between power and voltage.
Presets:
Input Mode
dBV Value
Voltage RMS
Impedance Optional
dBV is referenced to 1V RMS. If impedance is given, voltage can also be converted into power and dBm. Use Ω, kΩ or MΩ depending on your system/input impedance.
Presets:
Ratio Mode
Input / Reference
Output / Measured
dB Value
Use 10log for power ratios and 20log for voltage/current ratios. A 2× voltage gain is about +6.02dB; a 2× power gain is about +3.01dB.
Presets:
Audio / RF Mode
Level Value
Voltage Value
dBu is referenced to 0.775V RMS. dBµV is referenced to 1 microvolt and is common in RF/EMI signal-level work.
Presets:
📐 Formula Reference
dBm to Watts
P(W) = 10^((dBm - 30) / 10)
Watts to dBm
dBm = 10 × log10(P(W) / 0.001)
dBV to Volts
V = 10^(dBV / 20)
Voltage Gain in dB
dB = 20 × log10(Vout / Vin)
📋 Quick Reference
Common dBm
0 dBm1 mW
10 dBm10 mW
20 dBm100 mW
30 dBm1 W
Common Voltage Levels
0 dBV1 V
-20 dBV100 mV
0 dBu0.775 V
Ratio Rules
2× power+3.01 dB
2× voltage+6.02 dB
10× voltage+20 dB
📚 Engineering Notes
dB is not always powerUse 10log for power ratios. Use 20log for voltage or current ratios when impedance is the same.
dBm is absolute0dBm always means 1mW. 30dBm means 1W. Negative dBm means less than 1mW.
dBV is voltage referenced0dBV means 1V RMS. It does not include impedance unless you convert voltage to power using P = V²/R.
Audio noteProfessional audio often uses +4dBu. Consumer audio is often around -10dBV.
What is a dB / dBm / dBV Converter?
This converter helps translate between logarithmic signal levels and real electrical values. It is useful for RF power, amplifier gain, audio signal levels, sensor outputs and general electronics work.
dB vs dBm vs dBV
dB is a relative ratio. dBm is an absolute power referenced to 1 milliwatt. dBV is an absolute voltage referenced to 1 volt RMS.
❓ Frequently Asked Questions
0dBm is exactly 1 milliwatt, or 0.001 watts.
30dBm is 1 watt. Every +10dB means 10× power, so 20dBm is 100mW and 40dBm is 10W.
0dBV is exactly 1 volt RMS. -20dBV is 0.1V RMS, and +20dBV is 10V RMS.
Power is proportional to voltage squared when impedance is constant. Because of the square relationship, voltage and current ratios use 20log instead of 10log.
No. dBu is referenced to 0.775V RMS, while dBV is referenced to 1V RMS. 0dBu is about -2.21dBV.