dB / dBm / Watts Converter

RF power tool

Converter controls and results

Convert absolute RF power, then see how relative dB gain or loss changes it.

Quick power presets
RF power50 W
46.99 dBm16.99 dBW
Logarithmic RF power scale50 W · 46.99 dBm
−60 dBm1 nW−30 dBm1 µW0 dBm1 mW30 dBm1 W60 dBm1 kW

Every +10 dB multiplies power by 10. Every −10 dB divides it by 10.

0 dBm1 mW
10 dBm10 mW
20 dBm100 mW
30 dBm1 W
40 dBm10 W
50 dBm100 W

Common relative dB changes

+1 dB×1.259 power
−1 dB×0.794 power
+3 / −3 dBabout ×2 / ×½
+6 / −6 dBabout ×4 / ×¼
+10 dB×10 power
−10 dB×0.1 power

Understanding dB, dBm, dBW, and watts

Watts, dBm, and dBW are three ways to express an absolute power level. A value in dB by itself describes a relative gain or loss, not an absolute amount of power.

How the conversion works

dBW is referenced to one watt: dBW = 10 × log10(Pwatts). dBm is referenced to one milliwatt, so dBm = dBW + 30. The converter keeps one full-precision watt value internally while displaying practical rounded equivalents.

Why dB changes add

A relative change in dB represents a power ratio: power ratio = 10^(dB / 10). Multiple gains and losses can therefore be added in dB before that net change is applied to the starting power.

Common questions

Can dBm or dBW be negative? Yes. Negative logarithmic values describe positive power below the reference level. For example, −30 dBm is 1 µW.

Can watts be negative? Not in this RF power converter. Zero watts is represented as −∞ dBm and −∞ dBW.

Is dB the same as dBm? No. dBm is an absolute level referenced to 1 mW; dB is a relative ratio.

See how dB loss affects a real feedline → Coax Loss Calculator