mW-to-dBm / dBm-to-mW Power Conversion

Power is commonly expressed in decibel values in order to make adjustments due to loses and gains. The logarithmic nature of decibel units translates the multiplication and division associated with gains and losses into addition and subtraction. Once you get used to it, you will never want to return to watts. Units of dBm are decibels relative to 1 mW of power, hence, 0 dBm 1 mW. 1/100 mW is -20 dBm and 100 mW is +20 dBm. Powers less than 1 mW are always negative dBm values, and powers greater than 1 mW are always positive. See the graph below.

Here are the formulas:

P(mW) = 10^[P(dBm)/10]

P(dBm)=10*log[P(mW)]

RF Cafe - mW-to-dBm Power Conversion chart plot graph

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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a lady's voice announced "You've Got Mail" when a new message arrived...