How to Convert Watt Hours to Joules (and Joules to Watt Hours)

Have you ever looked at your electricity bill and wondered how those kilowatt-hours (kWh) or watt-hours (Wh) translate to actual energy in joules? If you need to know how to convert watt hours to joules, you are in the right place.

While watts measure power (the rate of energy use), watt-hours and joules both measure total energy. Converting between them is just a matter of scale.

The Converter Calculator

If you just need the answer right now, use our tool to instantly convert watt hours to joules or convert joules to watt hours.

The Formula: Watt Hours to Joules

To understand the conversion, you have to look at the definitions:

• 1 Watt = 1 Joule per second
• 1 Hour = 3,600 seconds

Therefore, 1 Watt-hour is simply 1 Watt of power sustained for 3,600 seconds. 1 Wh = 1 W × 3600 s = 3,600 Joules

Joules = Watt-hours × 3,600

Example Calculation

If a battery holds 50 Wh of energy and you need to convert watt hours to joules: 50 Wh × 3,600 = 180,000 Joules (or 180 kJ)

flowchart LR
    WH[Energy in Watt-hours] -- multiply by 3,600 --> J[Energy in Joules]
    style WH fill:#f9f,stroke:#333,stroke-width:2px
    style J fill:#bfb,stroke:#333,stroke-width:4px

How to Convert Joules to Watt Hours

To go in reverse and figure out how to convert joules to watt hours, simply divide the total number of joules by 3,600.

Watt-hours = Joules ÷ 3,600

If an impact driver uses 72,000 joules of energy to complete a job, and you want to convert joules to watt hours: 72,000 J ÷ 3,600 = 20 Wh

Quick Conversion Table

Here are some common conversions so you don't have to reach for a calculator:

The next time someone asks you how to convert watt hours to joules, just remember the magic number: 3,600.