Authoritative definitions of the International System of Units and SI prefixes.
Unit conversion
Joules to Watt-hours Converter
1 J ≈ 0.000277777777778 Wh. Enter a value to convert J to Wh, then use the formula and table below. Displayed digits may be rounded.
Energy, work, heat & powerInstant result
Decimals
Formula result = input × 1 ÷ 3600. 1 J ≈ 0.0003 Wh
Nonzero results too small for the selected decimal places use scientific notation.
Nonzero results too small for the selected decimal places use scientific notation.
Common examples
One value, several units
Kilojoules0.001 kJ
Megajoules1.00000e-6 MJ
Watt-hours0.0003 Wh
Kilowatt-hours2.77778e-7 kWh
Thermochemical calories0.239 cal
Kilocalories0.0002 kcal
BTU (International Table)0.0009 BTU
Conversion table
| J | Wh |
|---|---|
| 1 J | 0.0003 Wh |
| 2 J | 0.0006 Wh |
| 5 J | 0.0014 Wh |
| 10 J | 0.0028 Wh |
| 25 J | 0.0069 Wh |
| 50 J | 0.0139 Wh |
| 100 J | 0.0278 Wh |
Conversion chart
1 J0.0003 Wh
5 J0.0014 Wh
10 J0.0028 Wh
25 J0.0069 Wh
50 J0.0139 Wh
Worked example
1 J ≈ 0.000277777777778 Wh. Apply the selected conversion formula to other input values.
Unit definition
Joules (J) One joules equals 1 joule.
Unit history
The joule is named for James Prescott Joule and is the SI unit of energy, equal to one newton metre.
Step by step
1. Parse the value, including fractions.
2. Convert J to joule.
3. Convert the base value to Wh and apply your display precision.
Understand the result before using it
Joules to Watt-hours converts a value measured in Joules (J) into the equivalent value in Watt-hours (Wh). The numerical value changes because the size and definition of the selected unit changes; the underlying quantity does not.
Calculated result
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.
Formula, assumptions, and example
Formula
result = input × 1 ÷ 3600
Assumptions
- Joules and Watt-hours represent the same energy, work & heat quantity.
- The input is expressed in J; the output is expressed in Wh.
- The unit definitions and conventional relationship shown on this page apply.
Worked example
1 J ≈ 0.000277777777778 Wh. For another value, apply the same relationship and round only to the precision your source measurement supports.
When to use it
Good uses
- Read a J measurement in a document that expects Wh.
- Compare a joules value with a value reported in watt-hours.
- Check the J to Wh arithmetic before copying the result into another calculation.
Limitations
Common mistakes to avoid
- Do not confuse J with another unit that has a similar name or symbol.
- Round the output to a precision justified by the original measurement.
- Verify safety-critical, regulated, laboratory, and contractual conversions against the controlling standard.
Sources and further reading
These references explain the underlying standards or provide authoritative context. Your own contract, institution, clinician, product documentation, local code, or governing standard may be the controlling source.
Guidance on unit names, symbols, conversions, and numerical presentation.
Questions about this calculation
How do I convert Joules to Watt-hours?
result = input × 1 ÷ 3600. Input is in J; result is in Wh. 1 J ≈ 0.000277777777778 Wh. The displayed digits may be rounded.
What is 1 J in Wh?
1 J ≈ 0.000277777777778 Wh. The displayed digits may be rounded.
Can I reverse the J to Wh conversion?
Yes. Swap the source and target units in the converter. The reverse relationship converts Wh back to J.
Is the Joules to Watt-hours result exact?
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.