dBm to watts converter

Type a power level in dBm, such as 30, 23 or −70. The output gives it in watts; the rows give it in milliwatts, microwatts and dBW as well, and the steps show the formula with your number in it.

Swap the boxes to go from power to dBm. Type a power with its unit, such as 1 W, 250 mW or 5 µW; a plain number is read in the unit set under Power in.

dBm is power measured against one milliwatt on a logarithmic scale: P(mW) = 10^(dBm ÷ 10), and dBm = 10 × log10(P in mW). So 0 dBm is exactly 1 mW, 30 dBm is 1 W, and −30 dBm is 1 µW.

The scale turns multiplying into adding. Every +10 dB multiplies the power by 10 and every +3 dB very nearly doubles it, so a 20 dBm transmitter feeding an amplifier with 10 dB of gain puts out 30 dBm. Negative numbers aren't negative power, just less than a milliwatt: received radio signals are usually tiny, which is why phones and Wi-Fi tools show them as negative dBm.

dBW is the same idea measured against 1 watt instead of 1 milliwatt, so dBW = dBm − 30. Plain dB, with no letter after it, is a ratio between two powers, such as a gain or a loss, not a power level by itself.