A thermochemical calorie is 4.184 joules.
Calories to Watt-hours Converter — cal to Wh
Convert Calorie (cal) to Watt-hour (Wh) using the exact conversion factor (1 calorie = 0.0011622222 watt-hour). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Calories to Watt-hours converter
Converter
Engineering Converter
Convert common stress, force, torque, power, and energy units used in engineering.
Context values
Some unit families need one extra value for a physically accurate result.
A watt-hour is 3,600 joules.
Result = input x 4.184 / 3600.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Calories to Watt-hours
Calorie and Watt-hour both measure a quantity used in structural or mechanical engineering — commonly stress, pressure, force, torque, power, or energy — where converting between the unit conventions used in different regions, industries, or equipment specifications is a routine part of design work. Calorie is typically associated with nutrition labeling in the US and several other countries still commonly uses the kilocalorie (as 'Calorie'), while Watt-hour is typically associated with universal — standard consumer-electronics and battery energy unit worldwide.
Formula
watt-hours = calories × 0.00116222222222
This factor comes from each unit's defined relationship to the category's base unit: 1 calorie equals 4.184 base units, and 1 watt-hour equals 3600 base units, so dividing one by the other gives the direct calorie-to-watt-hour factor of 0.00116222222222.
Simple example
1 cal × 0.001162222222 = 0.0011622222 Wh
1 calorie = 0.0011622222 watt-hours.
Real-world example
100 cal × 0.001162222222 = 0.1162222222 Wh
100 calories = 0.1162222222 watt-hours.
Conversion table
| Calorie (cal) | Watt-hour (Wh) |
|---|---|
| 1 cal | 0.0011622222 Wh |
| 10 cal | 0.0116222222 Wh |
| 50 cal | 0.0581111111 Wh |
| 100 cal | 0.1162222222 Wh |
| 500 cal | 0.5811111111 Wh |
| 1,000 cal | 1.162222222 Wh |
Reverse conversion: Watt-hour to Calorie
0.0011622222 Wh × 860.4206501 = 0.9999999809 cal
0.0011622222 watt-hours = 0.9999999809 calories.
calories = watt-hours × 860.420650096
For a page dedicated to this direction, see Watt-hour to Calorie.
Calorie vs. Watt-hour
| Aspect | Calorie | Watt-hour |
|---|---|---|
| Family | Non-SI unit (limited use with SI) | metric derived energy unit |
| Typical use | Food energy labeling (as kilocalories, often written 'Calories') | Phone, laptop, and power-bank battery capacity ratings |
| Where it's used | Nutrition labeling in the US and several other countries still commonly uses the kilocalorie (as 'Calorie') | Universal — standard consumer-electronics and battery energy unit worldwide |
Understanding the Calorie
Calorie (cal) measures energy. The thermochemical calorie used in this converter is defined as exactly 4.184 joules. It is classified as a Non-SI unit (limited use with SI).
Where it's used: Nutrition labeling in the US and several other countries still commonly uses the kilocalorie (as 'Calorie')
Calorie vs. Calorie (kilocalorie). Food labels' capitalized 'Calorie' is actually one kilocalorie (1,000 small calories) — a long-standing labeling convention that causes frequent confusion.
Uses of the Calorie today
- Food energy labeling (as kilocalories, often written 'Calories')
- Historical chemistry and thermodynamics contexts
History of the Calorie
The calorie was originally defined in the early 19th century as the heat needed to raise one gram of water by one degree Celsius, but different scientific traditions defined it at slightly different reference temperatures, producing several close but non-identical 'calorie' values historically (15 °C calorie, mean calorie, thermochemical calorie).
To resolve this ambiguity, the thermochemical calorie was fixed by convention at exactly 4.184 joules; the very similar International Table calorie is fixed at exactly 4.1868 joules. The nutritional 'Calorie' seen on food labels is actually a kilocalorie (1,000 calories).
Historical origin. Calorie was not the invention of a single named person; it developed through the process described above.
Understanding the Watt-hour
Watt-hour (Wh) measures energy. The energy delivered by one watt of power sustained for one hour — equal to 3,600 joules. It is classified as a metric derived energy unit.
Where it's used: Universal — standard consumer-electronics and battery energy unit worldwide
Wh vs. kWh. The same unit at different scales: 1,000 Wh equals 1 kWh. Wh suits small consumer-electronics batteries; kWh is used for household electricity billing and larger energy storage.
Uses of the Watt-hour today
- Phone, laptop, and power-bank battery capacity ratings
- Electric-vehicle battery capacity specifications
- Small-scale renewable energy (solar panel) output ratings
Calorie — sources
- NIST Special Publication 811 — Documents the thermochemical calorie's exact joule equivalence.
Watt-hour — sources
- BIPM SI Brochure — Watt-hour as a common energy unit derived from the coherent SI units watt and second (via the hour).
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many watt-hours are in 1 calorie?
1 calorie equals 0.0011622222 watt-hours, using the exact defined conversion factor rather than an estimate.
How do I convert calorie to watt-hour?
Multiply the calorie value by 0.001162222222. The converter above does this instantly to whatever precision you set.
How do I convert watt-hour back to calorie?
Use the reverse factor: 1 watt-hour equals 860.4206501 calories. You can also use the swap control in the converter above to flip the direction instantly.
What is a calorie?
Calorie (cal) measures energy. The thermochemical calorie used in this converter is defined as exactly 4.184 joules. It is classified as a Non-SI unit (limited use with SI).
What is a watt-hour?
Watt-hour (Wh) measures energy. The energy delivered by one watt of power sustained for one hour — equal to 3,600 joules. It is classified as a metric derived energy unit.
Is the calorie to watt-hour conversion exact?
Yes. The thermochemical calorie used in this converter is defined as exactly 4.184 joules. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between calorie vs. calorie (kilocalorie)?
Food labels' capitalized 'Calorie' is actually one kilocalorie (1,000 small calories) — a long-standing labeling convention that causes frequent confusion.
Where is the calorie still used today?
Nutrition labeling in the US and several other countries still commonly uses the kilocalorie (as 'Calorie')