mW to dBm Converter

Formulas

Math: 10 * Log10(milliwatts / 1)

Javascript: var dbm = 10 * Math.log10(milliwatts / 1)

Python: dbm = 10 * math.log10(milliwatts / 1)

What is a Milliwatt?

A milliwatt is a thousandth of a watt. It is useful in measuring small amounts of power under 1 watt. That way, we don't need to describe a radio transmitter that emits 0.001 watts. 1000mW is equal to 1 watt. 

What is a dBm?

dBm is a unit of milliwatts measured in decibels. 1 Milliwatt is equal to 0 dBm, and with every 3 decibels (3dBm), the unit is doubled. Like wise, it also works in the reverse direction. -3 dBm is half of a milliwatt. You can even use dBm to measure signal levels at the radio receiver, although they are typically very weak at this point. A received signal at -70 dBm, for example, would be considered "strong" -- even though its 0.00000001 milliwatts! And for that reason, its a heck of a lot easier to write -70 dBm than a number with 7 zeros in front of it.