How many joules are in a kilowatt-hour?

One kilowatt-hour (kWh) equals exactly 3,600,000 joules (3.6 × 10⁶ J). This follows from the definition: 1 W = 1 J/s, and 1 hour = 3,600 s, so 1 kWh = 1,000 W × 3,600 s = 3,600,000 J.

How do I convert joules to kilowatt-hours?

Divide the number of joules by 3,600,000. For example, 7,200,000 J ÷ 3,600,000 = 2 kWh.

How do I convert kilowatt-hours to joules?

Multiply the number of kilowatt-hours by 3,600,000. For example, 0.5 kWh × 3,600,000 = 1,800,000 J.

What is a watt-hour (Wh) and how does it relate to joules?

A watt-hour equals 3,600 joules (1 W × 3,600 s). It is 1/1,000 of a kilowatt-hour. Battery capacities are often quoted in Wh, while electricity billing uses kWh.

Why are joules so small compared to kWh?

A joule is a very small amount of energy — roughly the energy needed to lift a 100 g object by 1 metre. A kilowatt-hour represents the energy drawn by a 1,000-watt appliance running for a full hour, making it 3.6 million times larger than a joule.

Is this conversion exact?

Yes. By SI definition, 1 kWh = 3.6 × 10⁶ J exactly. No approximation is involved.

Joules to Kilowatt Hours Converter

Convert joules to kilowatt-hours (or kWh to J) instantly — 1 kWh = 3,600,000 J exactly.

Energy Converter

Value in joules (J)

Kilowatt-hours (kWh)

—

Watt-hours (Wh) —

kWh = J ÷ 3,600,000

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Quick Reference Table

Joules (J)	kWh	Wh

kWh	Joules (J)	Wh

1 kWh = 3,600,000 J (exact) • 1 Wh = 3,600 J • 1 J = 2.77778×10^-7 kWh

Summary

Joules (J) are the SI derived unit of energy; kilowatt-hours (kWh) are the practical unit used by electricity meters and utility bills. One kilowatt-hour equals exactly 3,600,000 joules (3.6 MJ), because one watt = one joule per second and one hour = 3,600 seconds. To convert joules to kWh, divide by 3,600,000. To convert kWh to joules, multiply by 3,600,000. Watt-hours (Wh) sit in between: 1 Wh = 3,600 J, so 1 kWh = 1,000 Wh.

How it works

Select a conversion direction: J to kWh, or kWh to J.
Enter your energy value in the input field.
The result appears instantly in kWh and Wh (or J), with the formula shown.
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Use the reference table to look up common conversions at a glance.

Use cases

Convert physics or engineering energy values from joules to the kWh used on electricity bills.
Estimate battery capacity: convert joule ratings (e.g. from datasheets) into kWh.
Cross-check solar panel output figures given in joules against kWh meter readings.
Convert calorimetry or thermodynamics results into electrical energy equivalents.
Understand how many joules are stored in a 1 kWh home battery pack.
Verify unit conversions in science homework or exam problems.

Frequently Asked Questions

Last updated: 2026-06-19 · Reviewed by Nham Vu