Power conversion

Watts to dBm conversion

Convert with the free Watt to dBm on CalculatorX. Exact factors, formulas, worked examples, and a conversion chart. Runs locally in your browser.

Instant result

Result

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Enter values to convert.

Inputs —

Mode —

Formula —

Formulas

Core equations used by this converter.

FormuladBm = 10 × log10(P_W) + 30

iFollow the formulas shown. Calculation runs locally in your browser.

How to use

Convert watts to milliwatts (×1000).

Compute 10 × log₁₀(mW).

Result is dBm (power must be > 0).

## Related conversions

Example conversions

Common values with formula and result.

1 W to dBm

10 × log10(1) + 30 = 30 dBm

30 dBm

0.001 W to dBm

10 × log10(0.001) + 30 = 0 dBm

0 dBm

10 W to dBm

10 × log10(10) + 30 = 40 dBm

40 dBm

0.1 W to dBm

10 × log10(0.1) + 30 = 20 dBm

20 dBm

Watts to dBm conversion specification

Version 1.1.0 · Engine tested

Calculation status

Engine tested 4 published cases
Named expert review Not performed
Calculation version 1.1.0

Review policy

Definition: **Watt (W)** — linear SI power. **dBm** — logarithmic level vs 1 mW.
What it calculates: Convert watts (W) to dBm. Formula: dBm = 10 × log10(P_W) + 30. 1 W = 30 dBm. Examples and chart.
Inputs: Values required by the selected conversion mode
Outputs: Converted result in the target unit or format
Formula: dBm = 10 × log10(P_W) + 30
Watts to dBm conversion table: Watts (W) dBm
0.001 0
0.01 10
0.1 20
1 30
2 ≈33
10 40
100 50
1,000 60
Assumptions: Conversion runs locally in the browser; values are not uploaded.
Uses the formulas documented on this page.
Units: Formula
Boundary conditions: Empty or invalid input yields no valid result.
Out-of-range values may be rejected by the tool runtime.
Example: 1 W to dBm → 30 dBm
Validation cases: 1 W to dBm → 30 dBm
0.001 W to dBm → 0 dBm
10 W to dBm → 40 dBm
0.1 W to dBm → 20 dBm
Sources: CalculatorX converter runtime
Standard unit / encoding definitions where applicable
Calculation version: 1.1.0

Watts (W)	dBm
0.001	0
0.01	10
0.1	20
1	30
2	≈33
10	40
100	50
1,000	60

Background

Interpretation and common distinctions.

Use the converter tabs to switch direction when available. Results for Watts to dBm conversion update locally in your browser.

Frequently asked questions

Key distinctions behind the conversion.

How do you convert using Watts to dBm conversion?

Use dBm = 10 × log10(P_W) + 30. Example: 1 W to dBm → 30 dBm.

Can I switch direction?

Open the related reverse converter listed under Related tools.

Does this run online or locally?

Calculation runs locally in your browser. Values are not uploaded.

How precise are the results?

Results follow the formulas on this page. Round to the precision your use case needs.