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 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 kilowatt-hours to joules?

Multiply the number of kilowatt-hours by 3,600,000. For example, 5 kWh × 3,600,000 = 18,000,000 J (18 MJ).

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.

What is a megajoule (MJ) and how does it relate to kWh?

One megajoule equals 1,000,000 joules. Since 1 kWh = 3.6 MJ, a megajoule is about 0.2778 kWh. MJ is common in natural gas billing and thermal energy reporting.

What is a gigajoule (GJ) and how does it relate to kWh?

One gigajoule equals 1,000,000,000 joules (1,000 MJ). One GJ equals approximately 277.78 kWh. GJ is used for large-scale industrial energy and national energy statistics.

Is this conversion exact?

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

Kilowatt Hours to Joules Converter

Name: Kilowatt Hours to Joules Converter
Availability: InStock
Author: Nham Vu

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

Energy Converter

Value in kilowatt-hours (kWh)

Joules (J)

—

Scientific notation —

Megajoules (MJ) —

Gigajoules (GJ) —

J = kWh × 3,600,000

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Quick Reference Table

kWh	Joules (J)	MJ

Joules (J)	kWh	Wh

1 kWh = 3,600,000 J (exact) • 1 kWh = 3.6 MJ • 1 kWh ≈ 0.001 GJ • 1 J = 2.77778×10^-7 kWh

Practical Energy Context

LED bulb (1 hour)

0.01 kWh = 36,000 J

Laptop (1 hour)

0.05 kWh = 180,000 J

EV battery (small)

40 kWh = 144,000,000 J

Home battery pack

10 kWh = 36,000,000 J

Summary

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

How it works

Select a conversion direction: kWh to J, or J to kWh.
Enter your energy value in the input field.
The result appears instantly in joules (J), megajoules (MJ), and gigajoules (GJ), plus scientific notation.
Click Swap to reverse direction without clearing your value.
Use the reference table to look up common conversions at a glance.

Use cases

Convert electricity bill kWh readings into joules for physics homework or engineering calculations.
Estimate EV battery energy in joules from a kWh capacity rating.
Cross-check solar panel output figures between kWh and joule-based energy monitors.
Understand how many megajoules are stored in a home battery pack.
Verify energy unit conversions in thermodynamics or calorimetry problems.
Convert large joule values from scientific papers into the kWh used by utilities.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu