# Power Converter

> Converts power between watts (W to GW), mechanical horsepower (745.69987158227 W), metric horsepower (735.49875 W), BTU per hour, foot-pounds per second, kcal/h and tons of refrigeration.

- Calculator id: `power` · Category: Unit Conversion (`conversion`) · Tool name: `convert_power`
- Canonical page: https://tttkmbb.com/conversion/power · This document: https://tttkmbb.com/conversion/power.md · JSON definition: https://tttkmbb.com/conversion/power.json

## Purpose

Converts power between watts (W to GW), mechanical horsepower (745.69987158227 W), metric horsepower (735.49875 W), BTU per hour, foot-pounds per second, kcal/h and tons of refrigeration.

**Use when:** You need engine, motor, heater or air-conditioner power in another unit, e.g. hp to kW, kW to BTU/h or tons of refrigeration to kW.

**Do not use when:** You need energy (use energy) or to compute power from work and time or voltage and current (use work-power or electric-power).

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `value` | number |  | required | Amount to convert, expressed in from_unit. |
| `from_unit` | enum: W \| kW \| MW \| GW \| hp \| hp_metric \| BTU/h \| ft_lbf/s \| kcal/h \| ton_refrigeration |  | required | Unit of the input value. Accepted symbols: W, kW, MW, GW, hp, hp_metric, BTU/h, ft_lbf/s, kcal/h, ton_refrigeration; spelled-out names and common abbreviations are accepted too. |
| `to_unit` | enum: W \| kW \| MW \| GW \| hp \| hp_metric \| BTU/h \| ft_lbf/s \| kcal/h \| ton_refrigeration |  | required | Unit to convert into (same symbols as from_unit). |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `result` | number |  | Converted value expressed in to_unit (rounded to 6 decimals; see result_text for very small or very large values). |
| `result_text` | string |  | The conversion as text with 6 significant figures, e.g. "5 mi = 8.04672 km". |
| `formula` | string |  | Relation used, e.g. "1 mi = 1.609344 km". |
| `factor` | number |  | Multiplier from from_unit to to_unit (result = value × factor); absent for non-linear conversions. |
| `conversion_table` | object |  | The input value expressed in every supported power unit (6 significant figures), keyed by unit symbol. |

## Formula

`result = value × factor, factor = (1 from_unit in W) / (1 to_unit in W)`

hp is the mechanical (imperial) horsepower of 550 ft·lbf/s; hp_metric (PS, cv, ch) is 75 kgf·m/s. Electrical horsepower (746 W exactly) and boiler horsepower (9809.5 W) are not included.

## 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 2026-09-23)
- BIPM – The International System of Units (SI Brochure, 9th edition) — https://www.bipm.org/en/publications/si-brochure (standard, retrieved 2026-09-23)
- Wikipedia – Conversion of units — https://en.wikipedia.org/wiki/Conversion_of_units (reference, retrieved 2026-09-23)

Data freshness: `static`. Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output.

## API

- `GET https://tttkmbb.com/api/v1/calculate/power?value=…&from_unit=…&to_unit=…`
- `POST https://tttkmbb.com/api/v1/calculate/power` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/power · OpenAPI operationId `convert_power` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool:  `run_calculator` with `{"calculator_id": "power", "inputs": {…}}`

## Example

- 100 hp to kilowatts: inputs `{"value":100,"from_unit":"hp","to_unit":"kW"}` → `{"result":74.569987,"formula":"1 hp = 0.7456998716 kW","conversion_table":{"BTU/h":254443,"hp_metric":101.387}}`
- 2 kW to BTU per hour: inputs `{"value":2,"from_unit":"kW","to_unit":"BTU/h"}` → `{"result":6824.283,"conversion_table":{"hp":2.68204,"W":2000}}`

```
GET https://tttkmbb.com/api/v1/calculate/power?value=100&from_unit=hp&to_unit=kW
```

## Limitations

You need energy (use energy) or to compute power from work and time or voltage and current (use work-power or electric-power). hp is the mechanical (imperial) horsepower of 550 ft·lbf/s; hp_metric (PS, cv, ch) is 75 kgf·m/s. Electrical horsepower (746 W exactly) and boiler horsepower (9809.5 W) are not included. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Mechanical or metric horsepower?**

hp is the mechanical horsepower (745.7 W) used in the US and UK; hp_metric is the metric PS/cv/ch (735.5 W) used in European car specifications. They differ by 1.4%.

**What is a ton of refrigeration?**

The cooling rate that freezes one short ton of water in 24 hours: 12,000 BTU/h = 3516.85 W (3.517 kW).

## Related

- [Energy Converter](https://tttkmbb.com/conversion/energy.md) — Power × time gives energy (kWh, J).
- [Work & Power Calculator](https://tttkmbb.com/physics/work-power.md) — Compute power from work and time.
- [Electric Power Calculator](https://tttkmbb.com/physics/electric-power.md) — Power from voltage, current and resistance.