RF Power Converter & Calculator
Convert RF power between dBm, dBW, watts, milliwatts, microwatts, nanowatts and picowatts. Calculate RF voltage for known impedance and convert power, voltage and current ratios to dB.
This tool is focused on RF power conversion and dB ratio math. Full RF link budgets, cable transmission loss and propagation loss are handled by separate RF calculators.
Engineering tool
RF Power Converter & Calculator
Convert RF power between dBm, dBW and watts, calculate voltage-to-power for known impedance, and convert power, voltage, and current ratios to dB.
0 dBm equals 1 mW.
Result console
- dBm
- 0dBm
- dBW
- -30dBW
- Watts
- 0.001W
- milliwatts
- 1mW
- microwatts
- 1,000µW
- nanowatts
- 1,000,000nW
- picowatts
- 1e+9pW
- Engineering Unit
- 1 mW
- Scientific Notation
- 1e-3W
- Formula Used
- P(W) = 10^((dBm - 30) / 10)
Formula reference
RF Power and dB Formulas
Use absolute logarithmic units for RF power levels, and use dB only for relative ratios.
P(W) = 10^((dBm - 30) / 10)dBm = 10 × log10(P(W)) + 30P(W) = 10^(dBW / 10)dBW = 10 × log10(P(W))dBm = dBW + 30P = Vrms² / RVrms = √(P × R)Power ratio dB = 10 × log10(P2 / P1)Voltage ratio dB = 20 × log10(V2 / V1)Current ratio dB = 20 × log10(I2 / I1)Variable definitions
- dBm
- absolute power level referenced to 1 mW
- dBW
- absolute power level referenced to 1 W
- dB
- relative power, voltage or current ratio
- Vrms
- RMS voltage across the load
- R
- system or load impedance in ohms
- 50 Ω and 75 Ω are common RF system impedances
Worked Examples
0 dBm = 1 mW = 0.001 W.
30 dBm = 1 W.
40 dBm = 10 W.
1 W = 30 dBm.
20 W = 43.0103 dBm.
1 V RMS into 50 Ω gives P = 1² / 50 = 20 mW, or 13.0103 dBm.
Power ratio 100 gives 10log10(100) = 20 dB.
Voltage ratio 10 gives 20log10(10) = 20 dB.
Engineering Notes
- dB is not a power unit; it is a logarithmic ratio.
- dBm is referenced to 1 mW and is common for receiver sensitivity, signal generator output and low RF power levels.
- dBW is referenced to 1 W and is useful for higher-power transmitters.
- Power ratios use 10log10 because power is already proportional to energy flow.
- Voltage and current ratios use 20log10 only when impedance or reference conditions are equivalent.
- Voltage-to-power conversion requires impedance and assumes RMS voltage across a resistive or matched load.
- 50 Ω systems are common in RF test equipment, spectrum analyzers and signal generators.
- 75 Ω systems are common in video, CATV and some RF distribution systems.
Common Mistakes
- Treating dB as an absolute power unit.
- Using dBm and dB interchangeably.
- Using 10log10 for voltage ratio instead of 20log10.
- Using 20log10 for power ratio instead of 10log10.
- Converting voltage to dBm without specifying impedance.
- Forgetting that zero watts cannot be converted to dBm or dBW.
- Mixing peak voltage and RMS voltage in RF power calculations.
- Assuming RF power conversion replaces a full link budget or cable loss calculation.
Related RF Calculators
RF power conversion connects to the completed RF calculator suite for link, cable, propagation, and noise calculations.
Support reference
FAQ
What is dBm?
dBm is an absolute logarithmic RF power level referenced to 1 milliwatt. A value of 0 dBm equals 1 mW, 30 dBm equals 1 W, and negative dBm values represent powers below 1 mW.
What is dBW?
dBW is an absolute logarithmic power level referenced to 1 watt. A value of 0 dBW equals 1 W. For the same power level, dBm is 30 dB higher than dBW.
How do I convert dBm to watts?
Convert dBm to watts with P(W) = 10^((dBm - 30) / 10). For example, 30 dBm gives 10^0, or 1 watt.
Why is 0 dBm equal to 1 mW?
dBm is referenced to 1 milliwatt. Because 0 dB means a ratio of 1, 0 dBm means exactly 1 times the 1 mW reference.
What is the difference between dB and dBm?
dB is a relative ratio, while dBm is an absolute power level referenced to 1 mW. You can add dB gain or loss to a dBm power level, but dB alone is not a power unit.
Why does voltage use 20 log?
Voltage ratios use 20 log10 when the voltages are compared across the same impedance because power is proportional to voltage squared.
Why does power use 10 log?
Power ratios use 10 log10 because power is already the squared energy-flow quantity. Using 20 log10 for power ratios would double the dB result incorrectly.
Can I convert voltage to dBm without impedance?
No. Voltage-to-power conversion requires impedance because P = Vrms squared divided by R. RF systems commonly use 50 ohm or 75 ohm impedance.
Is this a complete RF link budget calculator?
No. This calculator handles RF power conversion and ratio math. A complete RF link budget also needs antenna gain, cable loss, path loss, fade margin, receiver sensitivity and other system terms.
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Future Engineering Guide Topics
Understanding dB
In_DevelopmentUnderstanding dBm
In_DevelopmentUnderstanding dBW
In_DevelopmentPower Ratio vs Voltage Ratio
In_Development50 Ω RF Systems
In_DevelopmentDisclaimer
This RF power calculator provides first-pass engineering conversions for RF power levels, impedance-based voltage and dB ratios. It does not replace RF safety review, regulatory compliance, spectrum measurement, impedance matching verification, thermal analysis or full RF link-budget design.