HP to kW and kW to HP Calculator
Convert mechanical horsepower, metric horsepower and kilowatts. With the formula, a worked example and typical values.
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Estimate only. Not engineering or safety advice. Check the result against the applicable standard and the equipment data, and have a competent engineer review it before it is relied on. Terms of use.
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About this calculator
This page calculates kilowatts, mechanical horsepower and metric horsepower from power. Change any value or its unit and the result updates. The steps below show the working for the default values, so you can check each line against your own method.
Limits of this calculator
Change the input unit to kW and read the other rows.
Cross-check: 10 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review.
Verification status: Engineering reference
Engineering reference. Formula and method documented and tested against separately coded reference calculations. Not yet Verified: the evidence listed on this page is still needed.
What this calculator checks
- The arithmetic of the published formula for the values you entered, in the units shown.
What remains unverified
- That the inputs suit your application. Take ratings, resistances and constants from the manufacturer data sheet or project specification.
Verification register entry
| Calculation author | Rahul Sharma (author) |
|---|---|
| Technical review | No independent technical review has been carried out |
| Individual professional approval | Not recorded |
| Formula reference | not recorded |
| Standard and edition | Not applicable: Mechanical horsepower to watt conversion is a unit conversion, not a standards-governed electrical design method. |
| Standard review state | Not applicable |
| Scope-screening note | not recorded |
| Cross-check test cases | 10 reference vectors (tests/reference_vectors.json) |
| Review date | not recorded |
| Next review date | not recorded |
| Status | Engineering reference |
Needed before this calculator can be marked Verified: reviewer name, qualification and review date; exact formula reference; formula source (textbook or standard); next review date.
Formula
Worked example
| Input | Value |
|---|---|
| Power | 100 HP |
- 100 HP = 74.57 kW = 101.387 PS
Assumptions
- HP is mechanical (550 ft·lbf/s)
- Electrical HP of 746 W differs by 0.04%
Change the input unit to kW and read the other rows.
Inputs and results
| Input | Unit | Allowed or shown | Note |
|---|---|---|---|
| Power | HP | greater than 0 HP |
| Result | Unit | Allowed or shown | Note |
|---|---|---|---|
| Kilowatts | kW | Shown to 3 decimal places | |
| Mechanical horsepower | HP | Shown to 3 decimal places | |
| Metric horsepower | PS | Shown to 3 decimal places |
How it is calculated
Each input is converted to the base unit of its quantity, the formula above is applied in the order shown in the worked example, and each result is shown in the unit you choose. Results are held at full precision and rounded only for display, except where a step selects a standard size, as the worked example shows. A value outside its allowed range is refused with a message instead of giving a result.
How the result changes with power
| Power (HP) | Kilowatts (kW) | Mechanical horsepower (HP) | Metric horsepower (PS) |
|---|---|---|---|
| 10 | 7.457 | 10 | 10.139 |
| 25 | 18.642 | 25 | 25.347 |
| 50 | 37.285 | 50 | 50.693 |
| 100 | 74.57 | 100 | 101.387 |
| 200 | 149.14 | 200 | 202.774 |
| 400 | 298.28 | 400 | 405.548 |
| 1,000 | 745.7 | 1,000 | 1,013.87 |
Other inputs are the same as in the worked example above.
Standards and further reading
These are textbook relationships (Ohm's law, series and parallel networks, AC phasors, three-phase quantities). No standard sets the method; standards apply when the result feeds a design, for example cable or protection selection.
Frequently asked questions
What do I need to enter?
Enter power. Change the unit of a value with its selector and the result stays the same.
What does this calculator assume?
HP is mechanical (550 ft·lbf/s). Electrical HP of 746 W differs by 0.04%.
Which calculators should I use next?
Common next steps are Motor Output Power and Efficiency Loss, Motor Full-Load Current and Power Unit Converter (W, kW, MW, HP, PS). The related links at the bottom of this page open them.
How accurate are the results?
Every figure comes from the same tested engine as the Elecmetric calculators and is meant for estimating. 10 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review. Check design values against the standard and the equipment data you work to.
Formula guides and reference
Longer explanations with worked examples and tables, written for the same topic.
- HP to kW Converter: mechanical horsepower to kilowatts
- kW to HP Converter: kilowatts to mechanical horsepower
- Induction Motor Formulas: Induction motor formulas for synchronous speed, slip, shaft torque and full-load current
More Electrical Fundamentals calculatorsAll engineering calculatorsHP to kW and kW to HP in Elecmetric