dBm ↔ Watts Conversion Calculator

Enter a value in dBm or power (W / mW) and click Calculate. Use Reset to clear. Precision and copy tools are provided.

Inputs

dBm value

dBm

Power

Tip: choose W or mW. 1 mW = 0 dBm.

Precision

Result: — dBm / — W / — mW

Examples:

dBm → Power Conversion Table

Power (dBm)	Power

Formulas dBm → mW: P_mW = 10^( P_dBm / 10 ) • mW → W: P(W) = P_mW / 1000 • W → dBm: P_dBm = 10 · log₁₀( 1000 · P(W) )

Understanding dBm and power conversion

Decibels (dB) express power ratios: dB = 10 · log₁₀( P / P_ref ). When the reference is 1 mW, we use dBm, an absolute power unit. So 0 dBm = 1 mW = 0.001 W and 30 dBm = 1 W.

Every +3 dB ≈ ×2 power; every +10 dB = ×10 power.
dBm is absolute power; dB alone is a ratio (gain/loss).
For voltage–power conversion, include system impedance: V = √( P · R ), where R is typically 50 Ω or 75 Ω.