Energy converter
Converts energy: J, kJ, MJ, Wh, kWh, and foot pounds-force.
99 Wh is 356.4 kJ.
- Input
Provenance
- Computed by
- units.energy.convert 1.0.0, core 0.1.0
- Model
- Exact unit definitions
- Accuracy
- Exact to double precision: each conversion is one correctly rounded ratio of exact definitions
- Notes
- None
- Cites
- National Institute of Standards and Technology, Guide for the Use of the International System of Units (SI), NIST Special Publication 811
Something look off?
How we got thisFormula, worked example, sources, and proof
Model: Exact unit definitions
Accuracy: Exact to double precision: each conversion is one correctly rounded ratio of exact definitions
When to use this: Use this when a capacity, a consumption or a quantity of work is quoted in one system and needed in another: a battery in watt hours against a limit in joules, a daily use in kilowatt hours against a supply in megajoules, a torque-wrench or fastener figure in foot pounds-force. Specification sheets and regulations each pick their own unit and rarely the same one.
Limitations: This converts energy, not power: a kilowatt hour is an amount of energy and a kilowatt is a rate, and the two are a quantity and its per-hour, so the power converter next door is the one for a rate. A foot pound-force of energy is numerically the same as a pound-foot of torque and is not the same thing -- torque is a moment, energy is work, and nothing here will stop you converting one as the other. Battery capacities quoted in mAh are a charge, not an energy, and need a voltage before they can come here; the charge converter handles those.
Worked example: 99 Wh in kilojoules. Source: Exact unit definitions (NIST SP 811 Appendix B). It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.
You enter
- To unit
- kJ
- Value
- 99 Wh
You get
- Converted
- 356.4 kJ
- Input
- 99 Wh
Review: Not yet independently reviewed by a metrologist.
Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.
Status: version 1.0.0, core 0.1.0. See this tool in the verification report.
Checked against: 34 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, National Institute of Standards and Technology, 2008 edition. Appendix B.8, Factors for units listed alphabetically.