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

The numbers on your electricity bill and the label on your power bank feel abstract until you connect them to actual energy. Here is the thing: watts measure power, but watt-hours (Wh) and joules (J) both measure the same thing — total energy. Converting between them is just a matter of scale.

Drop your numbers into the calculator below, or read on for the simple math.

The Formula: Watt Hours to Joules

Two facts do all the work here:

• 1 watt = 1 joule per second (1 W = 1 J/s)
• 1 hour = 3,600 seconds

Put them together and one watt-hour is one joule per second sustained for 3,600 seconds. That gives you:

Joules = Watt-hours × 3,600

So one watt-hour equals exactly 3,600 joules.

Example Calculation

Say you have a 50 Wh battery in a power bank. Multiply by the magic number:

50 Wh × 3,600 = 180,000 joules

That is the total energy the battery stores.

How to Convert Joules to Watt Hours

Going the other way, you divide by 3,600 instead of multiplying:

Watt-hours = Joules ÷ 3,600

If an impact driver uses 72,000 J to sink a batch of screws, that is 72,000 ÷ 3,600 = 20 Wh of energy drawn from the pack. Need the same math in the other direction? Our watt-hours to joules converter handles both.

Quick Conversion Table

Once the units click, the math never changes. A kilowatt-hour — the unit your utility bills you in — is just 1,000 watt-hours, or 3,600,000 joules. Want to work in kWh directly? Try the kWh to joules converter.