Convert Watts to Horsepower - Power Converter
This converter translates power expressed in kilowatts (kW) into horsepower (hp). It is intended for engineers, technicians, and consumers who need a reliable numeric conversion and clear guidance about which horsepower definition is being used.
Horsepower has multiple historical and practical definitions. By default this tool uses the commonly adopted mechanical (international) horsepower definition where 1 hp = 745.699872 watts. The page explains alternative hp definitions, the small numeric differences they produce, and when to select each for regulatory labeling or technical calculations.
Governance
Record c1f9d2208093 • Reviewed by Fidamen Standards Committee
Interactive Converter
Convert between kilowatt and horsepower with precision rounding.
Quick reference table
| Kilowatt | Horsepower |
|---|---|
| 1 kW | 1.341 hp |
| 5 kW | 6.705 hp |
| 10 kW | 13.41 hp |
| 25 kW | 33.526 hp |
| 50 kW | 67.051 hp |
| 100 kW | 134.102 hp |
Methodology
The conversion uses the fixed mathematical relationship between the watt (SI unit of power) and horsepower definitions. One kilowatt equals 1000 watts, and horsepower is defined as a specific number of watts depending on the horsepower type chosen. No empirical calibration is required for the arithmetic conversion itself.
For trustworthy unit definitions and guidance on unit usage we follow national and international standards and references including NIST guidance on units, the ISO quantities and units series, and IEEE recommendations where unit notation and electrical conventions apply. See citations for authoritative documents.
Users performing measurements for compliance, equipment specification, or lab reporting should consider measurement uncertainty and instrument calibration. The conversion preserves numerical precision but does not reduce measurement uncertainty associated with the source kW value.
Worked examples
Example 1: Convert 10 kW to mechanical horsepower. hp = 10 * 1000 / 745.699872 = 13.4102209 hp, typically reported as 13.41 hp.
Example 2: Convert 10 kW to metric horsepower (PS). hp(PS) = 10 * 1000 / 735.49875 = 13.5962162 PS, typically reported as 13.60 PS.
Example 3: Convert 5 kW using electrical horsepower (746 W). hp(electric) = 5 * 1000 / 746 = 6.7024129 hp, typically reported as 6.70 hp.
F.A.Q.
Which horsepower definition does this converter use by default?
The default is the mechanical (international) horsepower where 1 hp = 745.699872 W. This is commonly used in engineering contexts. Alternatives such as electrical horsepower (746 W) and metric horsepower (735.49875 W) are noted and may be selected where appropriate.
Why are there several horsepower values and which should I use for labeling?
Horsepower arose historically in different industries and countries, producing multiple conventions. Use the definition specified by the regulator, manufacturer guidance, or industry standard applicable to your jurisdiction. When in doubt for mechanical equipment, the international mechanical horsepower is widely accepted; for automotive contexts the metric horsepower (PS) is often used.
How precise is the conversion and what about measurement uncertainty?
The arithmetic conversion is exact given the defined constants, but the final reported precision should reflect the uncertainty of the input measurement. If the kW value comes from a meter or sensor, use the instrument's calibration uncertainty to determine appropriate significant digits for the converted hp value.
Can I convert back from horsepower to kilowatts?
Yes. Invert the same relationship: kW = hp * 745.699872 / 1000 for mechanical horsepower. Use the consistent horsepower definition for both directions to avoid mismatches.
Does the converter account for efficiency or losses?
No. This tool performs unit conversion only. When converting rated electrical power to mechanical output or vice versa, you must apply efficiency or loss factors separately based on measured or specified efficiency.
Are there regulatory requirements for reporting power ratings?
Yes. Equipment labeling and performance claims may be governed by regional regulations and industry standards. Ensure compliance with applicable standards and reference bodies such as national metrology institutes and industry-specific codes when publishing rated power.
Sources & citations
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI) — https://www.nist.gov/pml/special-publication-811
- ISO 80000 series - Quantities and units — https://www.iso.org/standard/30669.html
- IEEE Standards Association - Units notation and conventions — https://standards.ieee.org/
- OSHA - Machine guarding and safety guidance — https://www.osha.gov/machine-guarding
- BIPM - International Bureau of Weights and Measures, SI brochure and unit definitions — https://www.bipm.org/en/measurement-units/
Further resources
Related tools
External guidance
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
Record ID: c1f9d2208093What changed (latest)
v1.0.0 • 2025-11-18 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
What changed (latest)
v1.0.0 • 2025-11-18 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Engine
v1.0.0
Data
Baseline (no external datasets)
Content
v1.0.0
UI
v1.0.0
Governance
Last updated: Nov 18, 2025
Reviewed by: Fidamen Standards Committee (Review board)
Credentials: Internal QA
Risk level: low
Reviewer profile (entity)
Fidamen Standards Committee
Review board
Internal QA
Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person
Semantic versioning
- MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
- MINOR: New features or fields that do not change existing outputs for the same inputs.
- PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.
Review protocol
- Verify formulas and unit definitions against primary standards or datasets.
- Run golden-case regression suite and edge-case suite.
- Record reviewer sign-off with credentials and scope.
- Document assumptions, limitations, and jurisdiction applicability.
Assumptions & limitations
- Uses exact unit definitions from the Fidamen conversion library.
- Internal calculations use double precision; display rounding follows the unit's configured decimal places.
- Not a substitute for calibrated instruments in regulated contexts.
- Jurisdiction-specific rules may require official guidance.
Change log
v1.0.0 • 2025-11-18 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: b0edf2d55fc4