dBm vs Watts: a simple explanation with examples

Definition in one sentence

dBm expresses power on a logarithmic scale relative to 1 milliwatt, while Watts are linear power units.

Power conversion

$$P(W) = 10^{\frac{dBm-30}{10}}$$

Why RF uses dBm

Because gains/losses (dB) add/subtract easily in a link budget.

Quick reference points

• 0 dBm = 1 mW
• 10 dBm = 10 mW
• 20 dBm = 100 mW
• 30 dBm = 1 W

Practical example

If your transmitter is 20 dBm and your antenna adds +5 dBi, your EIRP is 25 dBm (ignoring losses).

Use a converter

• /conversion/... (wherever your dBm/W page lives today)

FAQ

Is dBm the same as dB?

No. dBm is absolute (referenced to 1 mW). dB is relative (ratio).