dBm to Watts Calculator
Convert dBm to milliwatts and watts (or watts back to dBm) — the decibel power scale used across RF, Wi-Fi and fibre.
How it works
P(mW) = 10^(dBm ÷ 10) · P(W) = P(mW) ÷ 1000 · dBm = 10 × log₁₀(P in mW) · dBW = dBm − 30
dBm is power expressed on a logarithmic scale referenced to 1 milliwatt, so 0 dBm is exactly 1 mW. Every 10 dB is a ten-fold change in power and every 3 dB roughly doubles or halves it. The log scale keeps huge dynamic ranges — from a −90 dBm Wi-Fi whisper to a +40 dBm transmitter — on one manageable axis.
Worked example
30 dBm converts as 10^(30 ÷ 10) = 1000 mW = 1 W. Dropping to 27 dBm halves it to about 0.5 W, and 0 dBm is exactly 1 mW.
Frequently asked questions
What does 0 dBm mean?
0 dBm is 1 milliwatt — the reference point of the scale. Positive dBm values are more than 1 mW and negative values are less; −30 dBm, for example, is 1 microwatt.
Why do engineers use dBm instead of watts?
Gains and losses along an RF chain simply add and subtract in decibels, whereas in watts you would multiply and divide. It also compresses an enormous range of powers into small, readable numbers.
How much is a good Wi-Fi signal in dBm?
Received signal strength around −50 dBm is excellent, −67 dBm is fine for streaming, and below about −80 dBm connections become unreliable. Remember these are negative because the received power is a tiny fraction of a milliwatt.
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This calculator is for educational purposes. Double-check important results before acting on them.