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Watts to dBm Conversion

Enter a power in watts and press Convert to see the same power in dBm. The table below lists eight watt values next to their dBm values, from 0.001 W at 0 dBm up to 1000 W at 60 dBm.

Using this converter

Type the power in watts into the single field — any amount above zero — and then press Convert. Nothing is worked out until you press it, and the dBm answer appears in a card below the button.

Copy writes the result together with its unit to the clipboard. Clear resets the form so you can start again with a new number.

Watts to dBm formula

P(dBm) = 10 × log10(P(W) × 1000), where P(W) is the power in watts. Power must be above zero.

Because the result goes through a logarithm, it is rounded to 15 significant digits and shown with ≈. The table is shortened, so the 2 W row lists 33.01029996 dBm.

Rows that come out even are also shown with ≈: 0.001 W is ≈ 0 dBm, 1 W is ≈ 30 dBm, and 1000 W is ≈ 60 dBm.