Unit conversion
Power Converter
Converts power, where horsepower has more than one definition.
Result
Conversions use exact internationally defined factors where one exists, so results are precise to the digits shown.
Get a Free Business AuditHow the calculation works
Each power unit multiplied by its factor relative to the watt. Horsepower is the complication, since mechanical horsepower is about 745.7 watts and metric horsepower about 735.5, which is a difference of roughly 1.4 per cent between figures quoted in the same word.
What moves the number
- Which horsepower definition applies.
- The factor for the unit pair.
- Whether the rating is input or output power.
- Tons of refrigeration in cooling contexts.
Where this one goes wrong
Input and output power are different ratings and the gap between them is the efficiency, which means a motor's input power draw and its output rating are not the same number and comparing one against the other overstates or understates capability. Check which the rating is. Cooling capacity in tons of refrigeration is the other sector-specific unit, deriving historically from ice melting rather than from any power unit.
Before you quote
- Establish which horsepower definition a figure uses.
- Distinguish input power draw from output rating.
- Note sector-specific units such as tons of refrigeration.
Questions
About this calculator
Is there more than one horsepower?
Yes. Mechanical horsepower is about 745.7 watts and metric horsepower about 735.5, a difference of roughly 1.4 per cent. Both are quoted as horsepower, which makes the figure ambiguous without knowing which definition applies.
Is a motor's rating its power draw?
Not usually. Output rating and input draw differ by the efficiency, so comparing one against the other misleads. Which a figure represents has to be established, particularly when sizing supply circuits or generators.
What is a ton of refrigeration?
A cooling capacity unit deriving historically from the rate of ice melting rather than from any power unit. It is standard in cooling equipment and converts to a specific number of watts or British thermal units per hour.
Common power conversions
| From | Equals |
|---|---|
| 1 Tons of refrigeration | 3,516.852842 Watts |
| 1 Tons of refrigeration | 3.516853 Kilowatts |
| 1 Tons of refrigeration | 0.003517 Megawatts |
| 1 Tons of refrigeration | 4.716177 Horsepower (mechanical) |
| 1 Tons of refrigeration | 4.781589 Horsepower (metric) |
| 1 Tons of refrigeration | 12,000 BTU per hour |
| 1 Tons of refrigeration | 1 Tons of refrigeration |
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How to use this calculator
- Value. Enter your own figure; the page starts at 3.
- From. Enter your own figure; the page starts at Tons of refrigeration.
- To. Enter your own figure; the page starts at BTU per hour.
The result updates as you type, so you can try a figure, see what it does to converted value, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Value | 3 |
| From | Tons of refrigeration |
| To | BTU per hour |
What comes out
| Result | Value |
|---|---|
| Converted value main result | 36,000 |
| Conversion factor | 12,000 |
3 Tons of refrigeration equals 36,000 BTU per hour.
How sensitive the answer is
Holding everything else steady and changing only value, this is what happens to converted value. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Value | Converted value |
|---|---|
| 1.5 | 18,000 |
| 2.25 | 27,000 |
| 3 example above | 36,000 |
| 4.5 | 54,000 |
| 6 | 72,000 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Value
- A number, starting at 3.
- From
- Choose from Watts, Kilowatts, Megawatts, Horsepower (mechanical), Horsepower (metric), BTU per hour, Tons of refrigeration.
- To
- Choose from Watts, Kilowatts, Megawatts, Horsepower (mechanical), Horsepower (metric), BTU per hour, Tons of refrigeration.
What the results tell you
| Result | What it is |
|---|---|
| Converted value | The headline result. A number. |
| Conversion factor | A number. |
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