# Horsepower (mechanical) to Watts (hp to W)

> Convert horsepower (mechanical) to watts: 1 hp = 745.7 W. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `hp-to-watts` · Quantity: Power (`power`, base unit W) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/hp-to-watts · This document: https://tttkmbb.com/conversion/hp-to-watts.md · JSON: https://tttkmbb.com/conversion/hp-to-watts.json (add `?value=` for a result)

## Formula

- `1 hp = 745.7 W`
- `watts = horsepower (mechanical) × 745.6998716`
- Reverse: `horsepower (mechanical) = watts × 0.00134102209`

The factor follows from the SI definitions of both units (NIST SP 811); values below are rounded to 6 significant figures, the API returns up to 12.

## Worked examples

- 5 hp = 3728.5 W
- 12.5 hp = 9321.25 W
- 100 hp = 74570 W

## Conversion table

| Horsepower (mechanical) (hp) | Watts (W) |
| --- | --- |
| 1 | 745.7 |
| 2 | 1491.4 |
| 3 | 2237.1 |
| 4 | 2982.8 |
| 5 | 3728.5 |
| 6 | 4474.2 |
| 7 | 5219.9 |
| 8 | 5965.6 |
| 9 | 6711.3 |
| 10 | 7457 |
| 15 | 11185.5 |
| 20 | 14914 |
| 25 | 18642.5 |
| 30 | 22371 |
| 40 | 29828 |
| 50 | 37285 |
| 75 | 55927.5 |
| 100 | 74570 |
| 200 | 149140 |
| 250 | 186425 |
| 500 | 372850 |
| 1000 | 745700 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=hp&to_unit=W` → unified JSON envelope with `result.values.result`, `formula`, `factor`, `sources`, `freshness`
- MCP: server `https://tttkmbb.com/mcp`, tool `convert_units` with `{"value":5,"from_unit":"hp","to_unit":"W"}`
- All power units: https://tttkmbb.com/api/v1/units?quantity=power · full converter: [Power Converter](https://tttkmbb.com/conversion/power.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many watts are in one horsepower?**

1 hp = 745.7 W. The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures.

**What is the formula to convert horsepower (mechanical) to watts?**

Multiply the value in horsepower (mechanical) by 745.6998716: watts = horsepower (mechanical) × 745.6998716. For example, 5 hp = 3728.5 W.

**How do I convert watts back to horsepower (mechanical)?**

Multiply by the inverse factor 0.00134102209 (horsepower (mechanical) = watts × 0.00134102209), or use the watts-to-horsepower (mechanical) page.

## Related conversions

- [Watts to horsepower (mechanical)](https://tttkmbb.com/conversion/watts-to-hp.md) (reverse)
- [Horsepower (mechanical) to Kilowatts](https://tttkmbb.com/conversion/hp-to-kw.md)
- [Kilowatts to Horsepower (mechanical)](https://tttkmbb.com/conversion/kw-to-hp.md)
- [Kilowatts to Watts](https://tttkmbb.com/conversion/kw-to-watts.md)
- [Watts to Kilowatts](https://tttkmbb.com/conversion/watts-to-kw.md)
- [BTU per hour to Watts](https://tttkmbb.com/conversion/btu-per-hour-to-watts.md)
- [Watts to BTU per hour](https://tttkmbb.com/conversion/watts-to-btu-per-hour.md)
- [Metric horsepower (PS) to Kilowatts](https://tttkmbb.com/conversion/ps-to-kw.md)
- [Kilowatts to Metric horsepower (PS)](https://tttkmbb.com/conversion/kw-to-ps.md)

## Data Sources

- NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors — https://www.nist.gov/pml/special-publication-811 (standard, retrieved 2026-09-24)
- BIPM – The International System of Units (SI Brochure, 9th edition) — https://www.bipm.org/en/publications/si-brochure (standard, retrieved 2026-09-24)
- Wikipedia – Conversion of units — https://en.wikipedia.org/wiki/Conversion_of_units (reference, retrieved 2026-09-24)