3 J to Wh — 3 joules in watt-hours
Exact 3 ÷ 3,600 = 0.000833333333
3 joules in other units
| Kilojoules | 0.003 | kJ |
|---|---|---|
| Megajoules | 0.000003 | MJ |
| Watt-hours | 0.000833333333 | Wh |
| Kilowatt-hours | 8.3333e-7 | kWh |
| Calories | 0.71701721 | cal |
| Kilocalories | 0.000717017208 | kcal |
| British thermal units | 0.002843451361 | BTU |
| Therms | 2.8435e-8 | thm |
| Foot-pounds | 2.212686 | ft·lbf |
| Electronvolts | 18,724,527,223,382,290,432 | eV |
J to Wh at a glance
| Joules | Watt-hours |
|---|---|
| 1 J | 0.000277777778 Wh |
| 2 J | 0.000555555556 Wh |
| 3 J | 0.000833333333 Wh |
| 5 J | 0.001388888889 Wh |
| 10 J | 0.002777777778 Wh |
| 20 J | 0.005555555556 Wh |
| 25 J | 0.006944444444 Wh |
| 50 J | 0.01388889 Wh |
| 100 J | 0.02777778 Wh |
| 250 J | 0.06944444 Wh |
| 500 J | 0.13888889 Wh |
| 1,000 J | 0.27777778 Wh |
How to convert joules to watt-hours
Multiply by 0.000277777778 — one joule is 0.000277777778 watt-hours. That factor is exact: it comes from the definition of the units rather than from a measurement, so it will not change and does not need rounding.
Working 3 ÷ 3,600 = 0.000833333333
What these units are
The joule and the watt-hour are covered in the energy unit guide, along with every other unit on this page.
Questions
How many watt-hours are in a joule?
One joule is 0.000277777778 watt-hours. This figure is exact — it comes from the definition of the unit, not a measurement.
What is 3 joules in watt-hours?
3 joules is 0.000833333333 watt-hours. The working is 3 ÷ 3,600 = 0.000833333333.
Is a food Calorie the same as a calorie?
No — it is a thousand of them. The Calorie on a nutrition label is a kilocalorie, written with a capital C in principle and almost never in practice. A 250 Calorie chocolate bar holds 250,000 physics calories, or about 1,046 kilojoules, which is why European labels quote kJ alongside.
What does a kilowatt-hour actually represent?
One kilowatt drawn for one hour — a 1,000 W heater running for sixty minutes, or a 100 W bulb for ten hours. It is the unit your electricity bill is priced in, and it equals exactly 3.6 million joules.
How much energy is one BTU?
Roughly the heat needed to raise one pound of water by one degree Fahrenheit — about 1,055 joules, or the energy in a single kitchen match. Air conditioners are rated in BTU per hour, where a 12,000 BTU/h unit is one "ton" of cooling and draws around 3.5 kW of heat.
Why is the electronvolt so small?
Because it is sized for single particles: it is the energy one electron picks up crossing a one-volt potential difference. At about 1.6 × 10⁻¹⁹ joules it would be absurd for anything larger, which is precisely why particle physics uses it instead of dragging around twenty leading zeros.