# Energy Converter

> Converts energy between joules (J to GJ), calories (thermochemical cal = 4.184 J, kcal), watt-hours (Wh, kWh, MWh), BTU (International Table, 1055.05585262 J), MMBTU, therm (EC), electronvolts, ergs and foot-pounds.

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

## Purpose

Converts energy between joules (J to GJ), calories (thermochemical cal = 4.184 J, kcal), watt-hours (Wh, kWh, MWh), BTU (International Table, 1055.05585262 J), MMBTU, therm (EC), electronvolts, ergs and foot-pounds.

**Use when:** You need an energy amount in another unit, e.g. kWh to MJ, kcal to kJ, BTU to kWh or therms to kWh for utility bills.

**Do not use when:** You need power (rate of energy, use power), the cost of electricity (use electricity-cost) or calories from macronutrient grams (use calories-from-macros).

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `value` | number |  | required | Amount to convert, expressed in from_unit. |
| `from_unit` | enum: J \| kJ \| MJ \| GJ \| erg \| cal \| kcal \| Wh \| kWh \| MWh \| BTU \| MMBTU \| therm \| eV \| ft_lbf |  | required | Unit of the input value. Accepted symbols: J, kJ, MJ, GJ, erg, cal, kcal, Wh, kWh, MWh, BTU, MMBTU, therm, eV, ft_lbf; spelled-out names and common abbreviations are accepted too. |
| `to_unit` | enum: J \| kJ \| MJ \| GJ \| erg \| cal \| kcal \| Wh \| kWh \| MWh \| BTU \| MMBTU \| therm \| eV \| ft_lbf |  | 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 energy unit (6 significant figures), keyed by unit symbol. |

## Formula

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

cal is the thermochemical calorie (4.184 J) and kcal the food Calorie (4184 J); BTU is the International Table BTU and therm the EC therm (100,000 BTU_IT). The International Steam Table calorie (4.1868 J) and US therm (105,480,400 J) differ by 0.07% and 0.02%.

## 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/energy?value=…&from_unit=…&to_unit=…`
- `POST https://tttkmbb.com/api/v1/calculate/energy` 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/energy · OpenAPI operationId `convert_energy` 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": "energy", "inputs": {…}}`

## Example

- 100 kWh to megajoules: inputs `{"value":100,"from_unit":"kWh","to_unit":"MJ"}` → `{"result":360,"factor":3.6,"formula":"1 kWh = 3.6 MJ","conversion_table":{"BTU":341214,"kcal":86042.1}}`
- 2000 kcal to kilojoules: inputs `{"value":2000,"from_unit":"kcal","to_unit":"kJ"}` → `{"result":8368,"factor":4.184,"conversion_table":{"kWh":2.32444,"BTU":7931.34}}`

```
GET https://tttkmbb.com/api/v1/calculate/energy?value=100&from_unit=kWh&to_unit=MJ
```

## Limitations

You need power (rate of energy, use power), the cost of electricity (use electricity-cost) or calories from macronutrient grams (use calories-from-macros). cal is the thermochemical calorie (4.184 J) and kcal the food Calorie (4184 J); BTU is the International Table BTU and therm the EC therm (100,000 BTU_IT). The International Steam Table calorie (4.1868 J) and US therm (105,480,400 J) differ by 0.07% and 0.02%. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Is a food Calorie the same as a calorie?**

A food Calorie (kcal, 'large calorie') is 1000 thermochemical calories (cal). Use kcal for nutrition labels.

**Which BTU is used?**

The International Table BTU (1055.05585262 J), the definition used by NIST SP 811 and in HVAC ratings. The thermochemical BTU (1054.35 J) is 0.07% smaller.

**How many kWh in a therm?**

29.3071 kWh (1 therm = 100,000 BTU = 105.5056 MJ).

## Related

- [Power Converter](https://tttkmbb.com/conversion/power.md) — Energy per unit time (W, hp, BTU/h).
- [Electricity Cost Calculator](https://tttkmbb.com/everyday/electricity-cost.md) — Cost of a kWh amount at a tariff.
- [Kinetic Energy Calculator](https://tttkmbb.com/physics/kinetic-energy.md) — Energy of a moving mass in joules.