Convert Milliwatts to BTU per Hour
1 milliwatt (mW) equals 0.003412141633 BTU per hour (BTU/h).
1 mW = 0.003412141633 BTU/h
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk milliwatt to BTU per hour converter to paste a column from Excel.
How to Convert Milliwatt to BTU per Hour
- 1 mW = 0.003412141633 BTU/h
- 1 BTU/h = 293.0710702 mW
- Example: convert 15 mW to BTU/h: 15 mW = 15 × 0.003412141633 BTU/h = 0.0511821245 BTU/h
Formula
BTU/h = mW × 0.003412141633128
or BTU/h = mW ÷ 293.0710701722
Derivation from SI units:
- 1 mW = 10⁻³ W
- 1 BTU/h = 1055.05585262 J ÷ 3600 s = 0.29307107 W
- 1 mW = 0.001 W ÷ 0.2930710701722 W per BTU/h = 0.003412141633128 BTU/h
Both units are defined exactly, so the factor is exact. Milliwatt definition: milliwatt; BTU per Hour definition: BTU per hour.
Worked examples
- A reading of 10 mW converts to 0.03412141633 BTU/h.
10 mW × 0.003412141633 = 0.03412141633 BTU/h - A value of 200 mW is 0.6824283266 BTU/h.
200 mW × 0.003412141633 = 0.6824283266 BTU/h
Milliwatt to BTU per Hour conversion table
| Milliwatts (mW) | BTU per Hour (BTU/h) |
|---|---|
| 0.1 mW | 0.0003412141633 BTU/h |
| 1 mW | 0.003412141633 BTU/h |
| 5 mW | 0.01706070817 BTU/h |
| 10 mW | 0.03412141633 BTU/h |
| 50 mW | 0.1706070817 BTU/h |
| 100 mW | 0.3412141633 BTU/h |
| 200 mW | 0.6824283266 BTU/h |
| 500 mW | 1.706070817 BTU/h |
| 1000 mW | 3.412141633 BTU/h |
Where it's used
Milliwatts are used for laser pointer and diode output, while BTU per hour appear in air-conditioner and heat-pump capacity (e.g. 12 000 BTU/h). Both measure power (energy per unit time), so the conversion is a fixed factor.
Milliwatt to other power units
| Conversion | 1 mW equals |
|---|---|
| milliwatt to watt | 0.001 W |
| milliwatt to kilowatt | 0.000001 kW |
| milliwatt to megawatt | 1 × 10⁻⁹ MW |
| milliwatt to horsepower | 0.00000134102209 hp |
| milliwatt to metric horsepower | 0.000001359621617 PS |
| milliwatt to BTU per hour | 0.003412141633 BTU/h |
| milliwatt to refrigeration ton | 2.843451361 × 10⁻⁷ TR |
| milliwatt to kilocalorie per hour | 0.0008598452279 kcal/h |
| milliwatt to foot-pound per second | 0.0007375621493 ft·lbf/s |
Frequently asked questions
How many BTU per hour are in 1 milliwatt?
1 mW = 0.003412141633 BTU/h.
How do I convert milliwatts to BTU per hour?
Multiply the value in mW by 0.003412141633, or divide it by 293.0710702. For example, 15 mW × 0.003412141633 = 0.0511821245 BTU/h.
Is the mW to BTU/h conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 7, SI prefixes.
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "British thermal unit_IT per hour".
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 Milliwatts to BTU per Hour. Retrieved October 17, 2026, from https://scientificconverters.com/power/milliwatts-to-btu-per-hour/
IEEE
Scientific Converters, "Convert Milliwatts to BTU per Hour," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/power/milliwatts-to-btu-per-hour/