About this tool
dBm / Watts / Volts Converter is a free, in-browser tool for RF and audio power levels. Pick the quantity you know — dBm, watts, milliwatts or volts RMS — enter its value and the impedance, and it returns all four quantities at once, with the one you entered shown first. Everything is computed locally; nothing is uploaded.
dBm is decibels relative to one milliwatt, so power in milliwatts is 10^(dBm ÷ 10) and dBm is 10 · log₁₀(P in mW). Watts are simply milliwatts ÷ 1000. Voltage depends on the load impedance Z: since power P = V² ÷ Z, the RMS voltage is √(P · Z). The impedance defaults to 50 Ω, the standard for most RF systems.
Use it to translate a transmitter's dBm rating into watts, work out the RMS voltage a power level produces across a known load, or check link-budget figures. Change Z to 75 Ω for video or 600 Ω for legacy audio lines.
Frequently asked questions
What is the difference between dBm and dB?
dBm is an absolute power level referenced to 1 milliwatt, so 0 dBm always means exactly 1 mW. Plain dB is a dimensionless ratio between two powers or voltages with no fixed reference — use the Decibel Gain / Ratio Calculator for those.
Why do I have to enter an impedance?
Power alone does not determine voltage — the same wattage produces different voltages across different loads. The tool needs Z to compute V = √(P · Z). dBm, watts and milliwatts are independent of impedance; only the voltage result depends on it.
What are some quick reference points?
0 dBm = 1 mW, 30 dBm = 1 W, 20 dBm = 100 mW, and −30 dBm = 1 µW. Every 10 dB is a ×10 change in power and every 3 dB is roughly double, which makes dBm handy for spanning huge power ranges.
Is anything uploaded?
No. All conversions happen in your browser, so power levels and impedances never leave your device and the tool works offline.
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