Joules to Watt-hours (J to Wh)

Formula

1 J = 0.000277778 Wh

watt-hours = joules × 0.0002777777778 — reverse: joules = watt-hours × 3600

The factor is derived from the SI definitions of both units (base unit: J) as listed in NIST SP 811; results on this page are shown to 6 significant figures, the API returns up to 12.

Worked examples

• 5 J = 0.00138889 Wh
• 12.5 J = 0.00347222 Wh
• 100 J = 0.0277778 Wh

Joules to watt-hours conversion table

FAQ

How many watt-hours are in one joule?

1 J = 0.000277778 Wh. 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 joules to watt-hours?

Multiply the value in joules by 0.0002777777778: watt-hours = joules × 0.0002777777778. For example, 5 J = 0.00138889 Wh.

How do I convert watt-hours back to joules?

Multiply by the inverse factor 3600 (joules = watt-hours × 3600), or use the watt-hours-to-joules page.

Related conversions

• Watt-hours to joules (reverse)
• Energy Converter — all energy units in one tool
• Kilocalories (food calories) to Kilojoules
• Kilojoules to Kilocalories (food calories)
• Joules to Calories (small, thermochemical)
• Calories (small, thermochemical) to Joules
• Kilowatt-hours to Megajoules
• Megajoules to Kilowatt-hours
• Kilowatt-hours to BTU
• BTU to Kilowatt-hours

Machine access

• API: GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=J&to_unit=Wh
• MCP: server https://tttkmbb.com/mcp, tool convert_units with {"value":5,"from_unit":"J","to_unit":"Wh"}
• Markdown: https://tttkmbb.com/conversion/joules-to-wh.md · JSON: https://tttkmbb.com/conversion/joules-to-wh.json (add ?value= for a result) · Units: /api/v1/units?quantity=energy
• OpenAPI operationId: convert_units. Freshness: static. Authentication: none.

Sources

• NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors (standard)
• BIPM – The International System of Units (SI Brochure, 9th edition) (standard)
• Wikipedia – Conversion of units (reference)