Authoritative definitions of the International System of Units and SI prefixes.
Unit conversion
Decibel-milliwatts to Watts Converter
1 dBm ≈ 0.00125892541179 W. Enter a value to convert dBm to W, then use the formula and table below. Displayed digits may be rounded.
Electrical unitsInstant result
Decimals
Formula result = 10^((input - 30) ÷ 10) ÷ 1. 1 dBm ≈ 0.0013 W
Nonzero results too small for the selected decimal places use scientific notation.
Nonzero results too small for the selected decimal places use scientific notation.
Common examples
One value, several units
Watts0.0013 W
Kilowatts1.25893e-6 kW
Megawatts1.25893e-9 MW
Conversion table
| dBm | W |
|---|---|
| 1 dBm | 0.0013 W |
| 2 dBm | 0.0016 W |
| 5 dBm | 0.0032 W |
| 10 dBm | 0.01 W |
| 25 dBm | 0.3162 W |
| 50 dBm | 100 W |
| 100 dBm | 10,000,000 W |
Conversion chart
1 dBm0.0013 W
5 dBm0.0032 W
10 dBm0.01 W
25 dBm0.3162 W
50 dBm100 W
Worked example
1 dBm ≈ 0.00125892541179 W. Apply the selected conversion formula to other input values.
Unit definition
Decibel-milliwatts (dBm) This unit is defined through the displayed non-linear relationship to watt.
Unit history
Decibel-milliwatts is represented here using its modern SI definition or an internationally accepted relationship to an SI base unit.
Step by step
1. Parse the value, including fractions.
2. Convert dBm to watt.
3. Convert the base value to W and apply your display precision.
Understand the result before using it
Decibel-milliwatts to Watts converts a value measured in Decibel-milliwatts (dBm) into the equivalent value in Watts (W). The numerical value changes because the size and definition of the selected unit changes; the underlying quantity does not.
Calculated result
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.
Formula, assumptions, and example
Formula
result = 10^((input - 30) ÷ 10) ÷ 1
Assumptions
- Decibel-milliwatts and Watts represent the same electrical power quantity.
- The input is expressed in dBm; the output is expressed in W.
- The unit definitions and conventional relationship shown on this page apply.
Worked example
1 dBm ≈ 0.00125892541179 W. For another value, apply the same relationship and round only to the precision your source measurement supports.
When to use it
Good uses
- Read a dBm measurement in a document that expects W.
- Compare a decibel-milliwatts value with a value reported in watts.
- Check the dBm to W arithmetic before copying the result into another calculation.
Limitations
Common mistakes to avoid
- Do not confuse dBm with another unit that has a similar name or symbol.
- Round the output to a precision justified by the original measurement.
- Verify safety-critical, regulated, laboratory, and contractual conversions against the controlling standard.
Sources and further reading
These references explain the underlying standards or provide authoritative context. Your own contract, institution, clinician, product documentation, local code, or governing standard may be the controlling source.
Guidance on unit names, symbols, conversions, and numerical presentation.
Questions about this calculation
How do I convert Decibel-milliwatts to Watts?
result = 10^((input - 30) ÷ 10) ÷ 1. Input is in dBm; result is in W. 1 dBm ≈ 0.00125892541179 W. The displayed digits may be rounded.
What is 1 dBm in W?
1 dBm ≈ 0.00125892541179 W. The displayed digits may be rounded. Use the full formula for other inputs; offset, reciprocal, and logarithmic scales cannot generally use this example as a multiplier.
Can I reverse the dBm to W conversion?
Yes. Swap the source and target units in the converter. The reverse relationship converts W back to dBm.
Is the Decibel-milliwatts to Watts result exact?
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.