# Electronvolts to Joules (eV to J)

> Convert electronvolts to joules: 1 eV = 1.60218e-19 J. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `ev-to-joules` · Quantity: Energy (`energy`, base unit J) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/ev-to-joules · This document: https://tttkmbb.com/conversion/ev-to-joules.md · JSON: https://tttkmbb.com/conversion/ev-to-joules.json (add `?value=` for a result)

## Formula

- `1 eV = 1.60218e-19 J`
- `joules = electronvolts × 1.602176634e-19`
- Reverse: `electronvolts = joules × 6241509074000000000`

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 eV = 8.01088e-19 J
- 12.5 eV = 2.00272e-18 J
- 100 eV = 1.60218e-17 J

## Conversion table

| Electronvolts (eV) | Joules (J) |
| --- | --- |
| 1 | 1.60218e-19 |
| 2 | 3.20435e-19 |
| 3 | 4.80653e-19 |
| 4 | 6.40871e-19 |
| 5 | 8.01088e-19 |
| 6 | 9.61306e-19 |
| 7 | 1.12152e-18 |
| 8 | 1.28174e-18 |
| 9 | 1.44196e-18 |
| 10 | 1.60218e-18 |
| 15 | 2.40326e-18 |
| 20 | 3.20435e-18 |
| 25 | 4.00544e-18 |
| 30 | 4.80653e-18 |
| 40 | 6.40871e-18 |
| 50 | 8.01088e-18 |
| 75 | 1.20163e-17 |
| 100 | 1.60218e-17 |
| 200 | 3.20435e-17 |
| 250 | 4.00544e-17 |
| 500 | 8.01088e-17 |
| 1000 | 1.60218e-16 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=eV&to_unit=J` → 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":"eV","to_unit":"J"}`
- All energy units: https://tttkmbb.com/api/v1/units?quantity=energy · full converter: [Energy Converter](https://tttkmbb.com/conversion/energy.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many joules are in one electronvolt?**

1 eV = 1.60218e-19 J. 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 electronvolts to joules?**

Multiply the value in electronvolts by 1.602176634e-19: joules = electronvolts × 1.602176634e-19. For example, 5 eV = 8.01088e-19 J.

**How do I convert joules back to electronvolts?**

Multiply by the inverse factor 6241509074000000000 (electronvolts = joules × 6241509074000000000), or use the joules-to-electronvolts page.

## Related conversions

- [Joules to electronvolts](https://tttkmbb.com/conversion/joules-to-ev.md) (reverse)
- [Kilocalories (food calories) to Kilojoules](https://tttkmbb.com/conversion/kcal-to-kj.md)
- [Kilojoules to Kilocalories (food calories)](https://tttkmbb.com/conversion/kj-to-kcal.md)
- [Joules to Calories (small, thermochemical)](https://tttkmbb.com/conversion/joules-to-calories.md)
- [Calories (small, thermochemical) to Joules](https://tttkmbb.com/conversion/calories-to-joules.md)
- [Kilowatt-hours to Megajoules](https://tttkmbb.com/conversion/kwh-to-mj.md)
- [Megajoules to Kilowatt-hours](https://tttkmbb.com/conversion/mj-to-kwh.md)
- [Kilowatt-hours to BTU](https://tttkmbb.com/conversion/kwh-to-btu.md)
- [BTU to Kilowatt-hours](https://tttkmbb.com/conversion/btu-to-kwh.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)