What is being measured?
Power is the rate of energy transfer. Power and energy differ by a time interval; watts and watt-hours cannot be exchanged by a unit factor alone.
Horsepower is mechanical unless marked metric. PS equals metric horsepower. Refrigeration tons use the US 12,000 BTU IT/h convention.
Meaning of mW
Milliwatts uses the symbol mW in this library and measures power. Under the stated reference convention, 1 mW = approximately 0.001 W. This equivalence changes how a known value is written. It does not increase measurement accuracy or establish whether a measurement is appropriate to a real application.
Conversion method
Multiply the value by the source factor (1e-3), then divide by the target factor (1). The factor ratio expresses the same power measurement in the other unit.
Worked example
For a known value of 10 mW, the reference conversion gives 0.01 W. Converting that result back gives approximately 10 mW. This reverse check helps catch a reversed factor, but matching round-trip arithmetic alone does not independently verify a source definition.
Common reference values
| Input (mW) | Reference equivalent (W) |
|---|---|
| 1 | 0.001 |
| 5 | 0.005 |
| 10 | 0.01 |
| 25 | 0.025 |
| 50 | 0.05 |
| 100 | 0.1 |
Compare one mW with other units
| Target unit | Equivalent of 1 mW | Definition guide |
|---|---|---|
| Watts (W) | 0.001 | Read definition |
| Kilowatts (kW) | 0.000001 | Read definition |
| Megawatts (MW) | 1e-9 | Read definition |
| btu per hour (BTU IT/h) | 0.00341214163313 | Read definition |
| Mechanical horsepower (hp mech) | 0.0000013410220896 | Read definition |
| metric horsepower (hp metric) | 0.0000013596216173 | Read definition |
| tons of refrigeration (TR) | 2.84345136094e-7 | Read definition |
| Nanowatts (nW) | 1000000 | Read definition |
Precision and common mistakes
- Keep the source and target quantity consistent. A matching symbol is not enough to establish a compatible definition.
- Record the original measurement precision. Showing twelve significant digits in a table does not make a rounded input more precise.
- Check symbol capitalization, prefixes and any regional convention in the source. Use the displayed unit definition rather than a similarly named unit.
- Factors involving repeating fractions or π use finite numerical precision. Round the final answer to the precision justified by your input.
Use a working converter
- Power converter
- Milliwatts to Watts converter
- Milliwatts to Kilowatts converter
- Milliwatts to Megawatts converter
- Milliwatts to btu per hour converter
- Milliwatts to Mechanical horsepower converter
Source and verification scope
Examples and tables are computed from the versioned unit definitions used by the linked converters. The source access dates appear below. Computandum is independent of the cited organizations; a citation does not mean that a publisher endorses this page or an actual project.
Sources
- NIST / BIPM: NIST: unit conversion factors ↗ · 2026-10-08