dBm to Watts Calculator

Convert dBm to watts (or dBm to mW) instantly—bidirectional RF/optical log power with chart references for wireless modules and radio links.

Quick formula: P(W) = 10^((dBm−30)/10) · P(mW) = 10^(dBm/10). Example: 30 dBm = 1 W; 0 dBm = 1 mW.

Calculator

Quick: dBm → W & mW. Advanced: reverse Power → dBm with W or mW units.

Conversion direction

Power level (dBm) Example: 20 dBm Wi-Fi AP class or 30 dBm = 1 W. Negative dBm allowed (receivers).

About this calculator

This dBm to watts calculator converts RF/optical log power ↔ W/mW. It is not a mains branch-circuit sizer—use Watts to Amps when you have linear watts plus voltage. Browse the power calculator hub.

Calculation Results

≈ 1 W (1,000 mW)

30 dBm → 1 W · 1,000 mW

Formula: P(W) = 10^((dBm − 30) / 10)

0 dBm = 1 mW by definition. This page owns dBm ↔ W / mW only—not dBW, VSWR, or antenna gain chains.

Continue Your Calculation

Have linear watts and a supply voltage? Estimate line current with Watts to Amps (not an RF matching tool).

Watts to Amps →

dBm to watts chart (0–50 dBm)

Common RF reference points. Click a row to load the calculator.

dBm	mW	W
	1	0.001
	10	0.01
	100	0.1
	1,000	1
	10,000	10
	100,000	100

dBm to watts formula

dBm → watts: P(W) = 10^{((dBm − 30) / 10)}

dBm → milliwatts: P(mW) = 10^{(dBm / 10)}

watts → dBm: dBm = 10 × log₁₀(W × 1000)

mW → dBm: dBm = 10 × log₁₀(mW)

0 dBm — 1 mW reference
30 dBm — 1 W
Use case — RF transmitters, wireless modules, optical power meters—not AC mains nameplates

Example: 20 dBm → 10^{((20−30)/10)} = 0.1 W (100 mW).

Need line current from watts? Watts to Amps. Hub: power calculator.

When to use which tool

Goal	Tool
Convert dBm ↔ W / mW (RF)	This page
Convert watts ↔ amps (mains)	Watts to Amps
Convert amps ↔ kW	Amps to kW
Convert W ↔ kW (×1000)	Power Hub W↔kW strip

Frequently Asked Questions

How do I convert dBm to watts?

Use P(W) = 10^{((dBm − 30) / 10)}. Example: 30 dBm = 1 W; 20 dBm = 0.1 W; 0 dBm = 0.001 W.

How do I convert dBm to milliwatts (mW)?

Use P(mW) = 10^{(dBm / 10)}. Example: 0 dBm = 1 mW; 10 dBm = 10 mW; 20 dBm = 100 mW. Reverse: pick mW under Power → dBm.

How much is 20 dBm in watts?

20 dBm = 0.1 W = 100 mW. Use the 20 dBm preset above.

How much is 1 watt in dBm?

1 W = 30 dBm. Choose Power → dBm and enter 1 W.

Is dBm the same as electrical mains watts?

No. dBm is a logarithmic RF/optical reference (0 dBm = 1 mW). For AC branch circuits use Watts to Amps with voltage and PF.

What is the difference between dBm and dBW?

dBm references 1 mW; dBW references 1 W. Relation: dBW = dBm − 30 (e.g. 30 dBm = 0 dBW = 1 W). This calculator outputs W/mW from dBm; convert to dBW by subtracting 30 if needed.