Convert Joules to Watt-hours
Convert Joules to Watt-hours instantly. 1 Joule (J) equals 0.0002778 Watt-hours (Wh).
Joules to Watt-hours conversion table
| Joules (J) | Watt-hours (Wh) |
|---|---|
| 1 J | 0.0002778 Wh |
| 2 J | 0.0005556 Wh |
| 3 J | 0.0008333 Wh |
| 5 J | 0.001389 Wh |
| 10 J | 0.002778 Wh |
| 20 J | 0.005556 Wh |
| 50 J | 0.01389 Wh |
| 100 J | 0.02778 Wh |
| 500 J | 0.1389 Wh |
| 1,000 J | 0.2778 Wh |
1 Joule = 0.0002778 Watt-hours · multiply Joules by 0.0002778
About converting Joules to Watt-hours
Joules (J) and Watt-hours (Wh) are both units of energy, so converting between them is a single multiplication: multiply your Joules figure by 0.0002778. Ten Joules comes to 0.002778 Watt-hours, and a hundred works out at 0.02778 Watt-hours.
Rule of thumb: going from Joules to Watt-hours divides, so the figure always shrinks — it takes about 3,600 Joules to make a single Watt-hour. If your answer came out bigger, you have the conversion the wrong way round.
What is a Joule?
The joule is the SI unit of energy and the reference every other energy unit here is defined against. One joule is one newton acting over one metre — push with a newton of force, move a metre, and you have spent a joule. It is named after James Prescott Joule, whose painstaking experiments established that heat and mechanical work are the same thing, measurable in the same units. That result sounds obvious now and was foundational then: it collapsed heat, motion and work into a single quantity called energy, which is why one unit can serve food, electricity, explosives and engines alike.
What is a Watt-hour?
A watt-hour is energy, not power, and that distinction trips people up constantly. A watt is a rate — energy per second — so a watt-hour is what you get by sustaining that rate for an hour: a quantity of energy expressed as "this much power for this long". It is the natural unit for anything that stores energy and releases it gradually, which is why phone and laptop batteries are rated in watt-hours rather than the milliamp-hours stamped on the cell, and why airlines police lithium batteries by their watt-hour rating. Capacity in watt-hours tells you how long a load can run; watts alone never can.
To put both in perspective: lifting an apple one metre takes about a joule, while a phone battery holds somewhere around 15 watt-hours.
The converter above updates as you type, and the table lists common values for quick reference. Need the opposite direction? Use the Watt-hours to Joules converter, or browse all Energy converters.
Frequently asked questions
How many Watt-hours are in one Joule?
There are 0.0002778 Watt-hours in one Joule.
How do I convert Joules to Watt-hours?
Multiply the number of Joules by 0.0002778. For example, 10 Joules = 0.002778 Watt-hours.
What is 100 Joules in Watt-hours?
100 Joules is equal to 0.02778 Watt-hours.
How do I convert Watt-hours to Joules?
Multiply the Watt-hours value by 3,600 (or divide by 0.0002778).
Is this Joules to Watt-hours conversion exact?
The definition is exact — Joules and Watt-hours are both fixed against the same base by international agreement — but the decimal shown here is rounded for readability, because the true ratio does not terminate. For engineering or scientific work, carry more decimal places than this page displays.
What is a Joule?
The joule is the SI unit of energy and the reference every other energy unit here is defined against. One joule is one newton acting over one metre — push with a newton of force, move a metre, and you have spent a joule. It is named after James Prescott Joule, whose painstaking experiments established that heat and mechanical work are the same thing, measurable in the same units. That result sounds obvious now and was foundational then: it collapsed heat, motion and work into a single quantity called energy, which is why one unit can serve food, electricity, explosives and engines alike.
What is a Watt-hour?
A watt-hour is energy, not power, and that distinction trips people up constantly. A watt is a rate — energy per second — so a watt-hour is what you get by sustaining that rate for an hour: a quantity of energy expressed as "this much power for this long". It is the natural unit for anything that stores energy and releases it gradually, which is why phone and laptop batteries are rated in watt-hours rather than the milliamp-hours stamped on the cell, and why airlines police lithium batteries by their watt-hour rating. Capacity in watt-hours tells you how long a load can run; watts alone never can.