Convert Watts to Milliwatts
1 watt (W) equals 1000 milliwatts (mW).
1 W = 1000 mW
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk watt to milliwatt converter to paste a column from Excel.
How to Convert Watt to Milliwatt
- 1 W = 1000 mW
- 1 mW = 0.001 W
- Example: convert 15 W to mW: 15 W = 15 × 1000 mW = 15000 mW
Formula
mW = W × 1000
Derivation from SI units:
- 1 W = 1 J/s = 1 kg·m²·s⁻³
- 1 mW = 10⁻³ W
Both units are defined exactly, so the factor is exact. Watt definition: watt; Milliwatt definition: milliwatt.
Worked examples
- A reading of 100 W converts to 100000 mW.
100 W × 1000 = 100000 mW - A value of 1500 W is 1500000 mW.
1500 W × 1000 = 1500000 mW
Watt to Milliwatt conversion table
| Watts (W) | Milliwatts (mW) |
|---|---|
| 1 W | 1000 mW |
| 5 W | 5000 mW |
| 10 W | 10000 mW |
| 40 W | 40000 mW |
| 60 W | 60000 mW |
| 100 W | 100000 mW |
| 250 W | 250000 mW |
| 500 W | 500000 mW |
| 746 W | 746000 mW |
| 1000 W | 1000000 mW |
| 1500 W | 1500000 mW |
| 2000 W | 2000000 mW |
| 3500 W | 3500000 mW |
| 5000 W | 5000000 mW |
| 10000 W | 10000000 mW |
Where it's used
Watts are used for electrical appliance ratings, while milliwatts appear in laser pointer and diode output. Both measure power (energy per unit time), so the conversion is a fixed factor.
Watt to other power units
| Conversion | 1 W equals |
|---|---|
| watt to milliwatt | 1000 mW |
| watt to kilowatt | 0.001 kW |
| watt to megawatt | 0.000001 MW |
| watt to horsepower | 0.00134102209 hp |
| watt to metric horsepower | 0.001359621617 PS |
| watt to BTU per hour | 3.412141633 BTU/h |
| watt to refrigeration ton | 0.0002843451361 TR |
| watt to kilocalorie per hour | 0.8598452279 kcal/h |
| watt to foot-pound per second | 0.7375621493 ft·lbf/s |
Frequently asked questions
How many milliwatts are in 1 watt?
1 W = 1000 mW.
How do I convert watts to milliwatts?
Multiply the value in W by 1000. For example, 15 W × 1000 = 15000 mW.
Is the W to mW conversion exact?
Yes. Both units are defined exactly, and 1 W is exactly 1000 mW.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4, coherent derived units with special names.
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 7, SI prefixes.
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Watts to Milliwatts. Retrieved October 17, 2026, from https://scientificconverters.com/power/watts-to-milliwatts/
IEEE
Scientific Converters, "Convert Watts to Milliwatts," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/power/watts-to-milliwatts/