Unit Converters · Browser · Free

mW to dBm Conversion

Enter a power in milliwatts and read the same power expressed in dBm. Because the conversion uses a logarithm, results are rounded to 15 significant digits and shown with ≈.

What this converter does

This tool takes a power given in milliwatts and writes that same power in dBm. There is one number field for the input, and nothing else to fill in.

The conversion runs when you press Convert, and the answer appears in a card below the button. Press Copy to put the result together with its unit on your clipboard, or Clear to reset the form. All of it happens locally in the browser and nothing is uploaded.

The mW to dBm formula

P(dBm) = 10 × log10(P(mW)). Take the base-10 logarithm of the power in milliwatts and multiply it by 10. The power you enter must be above zero.

The reference table works a few values out in advance: 1 mW is listed as 0 dBm, 10 mW as 10 dBm, and 100 mW as 20 dBm, so each step of ten times the power in milliwatts lines up with ten more dBm. A value in between, such as 2 mW, is listed as 3.010299957 dBm.