Convert Milliwatts to BTU per hour
1 milliwatt is 0.003412 BTU/h. One milliwatt is exactly 0.00341214163313 BTU per hour.
One milliwatt is 0.0034121416 BTU per hour. To convert milliwatts to BTU per hour, multiply by 0.0034121416; to go the other way, divide by 0.0034121416 or multiply by 293.07107. The relation is exact but the figure is not: it is a rounding of a number that does not terminate, and it follows from NIST Special Publication 811. A thousandth of a watt.
Factor checked against the defining standard · How we check
- Milliwatts × 0.0034121416
1 * 0.00341210.003 BTU/h
1 milliwatt in every power unit
| Unit | Value | Exact factor |
|---|---|---|
| horsepower | 0.00000134102209 hp | × 0.0000013410220896 |
| metric horsepower | 0.000001359621617 PS | × 0.0000013596216173 |
| watts | 0.001 W | × 0.001 |
| kilowatts | 0.000001 kW | × 0.000001 |
| milliwatts (as entered) | 1 mW | — |
| megawatts | 0.000000001 MW | × 0.000000001 |
| tons of refrigeration | 0.0000002843451361 TR | × 0.000000284345136094 |
| BTU per hour | 0.003412141633 BTU/h | × 0.00341214163313 |
Factors are entered by hand from NIST Special Publication 811 rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert milliwatts to BTU per hour? The converter and the working
- 1.Take the measurement in milliwatts.
- 2.Multiply by 0.0034121416 — that is how many BTU per hour fit in one milliwatt.
- 3.To go back the other way, divide by 0.0034121416, or multiply by 293.07107.
Worked example: 25 milliwatts to BTU per hour
- Formula
- mW × 0.0034121416 = BTU/h
- Arithmetic
- 25 × 0.0034121416 = 0.09 BTU/h
- Answer
- 25 mW = 0.09 BTU/h
The factor is rounded for display; the figure above is computed from the full value.
Milliwatts to BTU per hour conversion table
| Milliwatts | BTU per hour |
|---|---|
| 1 mW | 0.003412 BTU/h |
| 2 mW | 0.01 BTU/h |
| 3 mW | 0.01 BTU/h |
| 4 mW | 0.01 BTU/h |
| 5 mW | 0.02 BTU/h |
| 6 mW | 0.02 BTU/h |
| 7 mW | 0.02 BTU/h |
| 8 mW | 0.03 BTU/h |
| 9 mW | 0.03 BTU/h |
| 10 mW | 0.03 BTU/h |
| 12 mW | 0.04 BTU/h |
| 15 mW | 0.05 BTU/h |
| 20 mW | 0.07 BTU/h |
| 25 mW | 0.09 BTU/h |
| 50 mW | 0.17 BTU/h |
| 100 mW | 0.34 BTU/h |
| 200 mW | 0.68 BTU/h |
| 300 mW | 1.02 BTU/h |
| 500 mW | 1.71 BTU/h |
| 1000 mW | 3.41 BTU/h |
| 2000 mW | 6.82 BTU/h |
| 5000 mW | 17.06 BTU/h |
| 10000 mW | 34.12 BTU/h |
What is a milliwatt?
A thousandth of a watt. Radio transmit power, laser output and audio signal levels are all quoted in it, and dBm is referenced to exactly one.
What is a BTU per hour?
The rate US heating and air conditioning is sold in. A 12,000 BTU/h unit is one "ton" of cooling and about 3.5 kilowatts of heat moved.
How many BTU per hour are in a milliwatt?
One milliwatt is 0.0034121416 BTU per hour. Going the other way, one BTU per hour is 293.07107 milliwatts. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every power unit here
The whole group — 8 units with their symbols and the size of each one in watts — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to a milliwatt.
Source: NIST Special Publication 811 — mechanical horsepower is 550 ft·lbf/s exactly
Cite this page
- APA
- Rule Calculator. (2026). Convert Milliwatts to BTU per hour. Rule Calculator. https://rulecalculators.com/convert/milliwatt-to-btu-per-hour
- MLA
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- Chicago
- Rule Calculator. "Convert Milliwatts to BTU per hour." Rule Calculator. Last reviewed August 16, 2026. https://rulecalculators.com/convert/milliwatt-to-btu-per-hour.
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Questions people actually ask
- How many BTU per hour are in a milliwatt?
- 0.0034121416. The rate US heating and air conditioning is sold in. A 12,000 BTU/h unit is one "ton" of cooling and about 3.5 kilowatts of heat moved.
- How do I convert BTU per hour back to milliwatts?
- Divide by 0.0034121416, or multiply by 293.07107 — they are the same operation.
Other power conversions
BTU per hour to milliwatts — the same conversion the other way.