Authoritative definitions of the International System of Units and SI prefixes.
Unit converters
Energy, work & power converter
Convert energy, work & power units including J, kJ, MJ, Wh, kWh, cal. See the formula, conversion tables and examples for your selected units.
Energy, work, heat & powerInstant result
Decimals
Formula result = input × 1 ÷ 1000. 1 J = 0.001 kJ
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 | kJ |
|---|---|
| 1 J | 0.001 kJ |
| 2 J | 0.002 kJ |
| 5 J | 0.005 kJ |
| 10 J | 0.01 kJ |
| 25 J | 0.025 kJ |
| 50 J | 0.05 kJ |
| 100 J | 0.1 kJ |
Conversion chart
1 J0.001 kJ
5 J0.005 kJ
10 J0.01 kJ
25 J0.025 kJ
50 J0.05 kJ
Worked example
1 J = 0.001 kJ. 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 kJ and apply your display precision.
Understand the result before using it
Energy, work & power converts energy, work, heat, or power within the matching quantity group. 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 ÷ 1000
Assumptions
- The source and target selections represent the same physical quantity or supported notation.
- The entered value is valid for the selected relationship and uses the source unit shown.
- Published unit definitions and conventional conversion factors apply under their stated conditions.
Worked example
1 kilowatt-hour equals exactly 3.6 megajoules.
When to use it
Good uses
- Translate a energy, work & power value found in a document, specification, recipe, or measurement.
- Compare values reported in different unit systems.
- Check a manual conversion and control the displayed precision.
Limitations
Common mistakes to avoid
- Unit conversion does not account for measurement uncertainty, instrument calibration, or context outside the unit definition.
- Do not add meaningful digits beyond the precision of the original measurement.
- Confirm regulated, safety-critical, laboratory, and contractual values 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
What does the Energy, work & power converter do?
Energy, work & power converts energy, work, heat, or power within the matching quantity group. It does not change the physical quantity represented by the input.
What formula does the Energy, work & power converter use?
result = input × 1 ÷ 1000
Why can a Energy, work & power converter result be rounded?
UnitMora calculates with JavaScript double-precision numbers, then formats the result using your selected decimal or significant-figure setting. The unrounded value may contain more digits than are displayed.
What is the most common energy, work & power conversion mistake?
The most common mistake is selecting a similarly named but different unit or treating a rounded measurement as exact.
Energy, work & power conversion tables
Open a unit pair for its formula, worked example and reference table.
- Joules to Kilojoules
- Kilojoules to Joules
- Joules to Megajoules
- Megajoules to Joules
- Joules to Watt-hours
- Watt-hours to Joules
- Joules to Kilowatt-hours
- Kilowatt-hours to Joules
- Joules to Thermochemical calories
- Thermochemical calories to Joules
- Joules to Kilocalories
- Kilocalories to Joules
- Joules to BTU (International Table)
- BTU (International Table) to Joules
- Watts to Kilowatts
- Kilowatts to Watts
- Watts to Megawatts
- Megawatts to Watts
- Watts to Mechanical horsepower
- Mechanical horsepower to Watts
- Watts to Metric horsepower
- Metric horsepower to Watts
- Watts to BTU per hour
- BTU per hour to Watts
Clear answers, without the guesswork
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