Convert Calories per Second to Watts
Calorie per Second (cal/s) to Watt (W) unit conversion — enter any value below to get an instant result, or use the table for common values.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
1 cal/s = 4.1868 W
1 Calorie per Second = 4.1868 Watts
1 Watt = 0.2388459 Calories per Second
1 cal/s in every supported unit
Conversion chart: Calorie per Second to Watts
Conversion table
| Calorie per Second (cal/s) | Watt (W) |
|---|---|
| 0.01 cal/s | 0.041868 W |
| 0.1 cal/s | 0.41868 W |
| 1 cal/s | 4.1868 W |
| 2 cal/s | 8.3736 W |
| 3 cal/s | 12.5604 W |
| 5 cal/s | 20.934 W |
| 10 cal/s | 41.868 W |
| 20 cal/s | 83.736 W |
| 50 cal/s | 209.34 W |
| 100 cal/s | 418.68 W |
| 1000 cal/s | 4186.8 W |
Calorie per Second (cal/s)
Definition: The rate of transferring one (small) calorie of heat energy — the energy needed to raise one gram of water by one degree Celsius — every second, equal to exactly 4.1868 watts.
History: Derived from the calorie, a unit of heat energy defined in the early 19th century by French physicist Nicolas Clément, later tied exactly to the joule (1 cal = 4.1868 J) once the SI system was established.
Current use: Occasionally used in thermal and biological contexts, such as expressing metabolic power output or heat-transfer rates in laboratory and physiology settings, where energy is already tracked in calories.
Watt (W)
Definition: The SI derived unit of power, defined as one joule of energy transferred per second (1 W = 1 J/s).
History: Named in 1882 by the British Association for the Advancement of Science in honor of Scottish engineer James Watt, whose improvements to the steam engine in the 1760s-1780s made mechanical power practical on an industrial scale. The unit was formally adopted into the SI system in 1960.
Current use: The universal base unit for electrical and mechanical power worldwide — light bulb wattage, phone charger output, and appliance power ratings are all expressed in watts on every continent.
Supported Units
| Unit | Symbol | In Watts |
|---|---|---|
| Milliwatt | mW | 0.001 W |
| Watt | W | 1 W |
| Kilowatt | kW | 1000 W |
| Megawatt | MW | 1000000 W |
| Gigawatt | GW | 1E+09 W |
| Horsepower (mechanical) | hp | 745.69987 W |
| Horsepower (metric) | PS | 735.49875 W |
| BTU per Hour | BTU/h | 0.29307107 W |
| Foot-pound per Second | ft·lb/s | 1.3558179 W |
| Calorie per Second | cal/s | 4.1868 W |
About These Parameters
- Value
- The number you want to convert, expressed in the "From" unit. Accepts decimals.
- From Unit
- The unit your input value is currently measured in.
- To Unit
- The unit you want the result converted into. Use the swap button to flip From and To instantly.
How Power Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to the watt. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Calorie per Second → Watt: multiply by 4.1868. For example, 1 cal/s × 4.1868 = 4.1868 W.
Mechanical vs. Metric Horsepower
The two horsepower units on this page look almost identical but are not quite the same: mechanical horsepower (hp) is defined as exactly 550 foot-pounds of work per second (about 745.7 W) and is the standard for cars and engines in the US and UK, while metric horsepower (PS, from the German Pferdestärke) is defined as the power to lift 75 kilograms one meter per second (about 735.5 W) and is used across continental Europe, Japan, and much of Asia. The difference is small — about 1.4% — but it means a car advertised as "300 PS" in Germany produces slightly less power than a car advertised as "300 hp" in the US, even though the numbers look the same.
How James Watt Defined Horsepower
In the 1780s, engineer James Watt needed a way to convince mill owners that his improved steam engines could outperform the horses they already used to turn grinding wheels. He observed a strong horse turning a mill and calculated it could sustain roughly 33,000 foot-pounds of work per minute — equivalent to 550 foot-pounds per second — and fixed that figure as "one horsepower." The unit stuck long after steam engines and horses both gave way to electric and internal combustion power, and it remains the standard way vehicle and engine power is marketed today.
Example
1 cal/s equals 4.1868 W. For scale, that's about 0× the power draw of a typical microwave oven (1,000 W, or 238.8459 cal/s).
Frequently Asked Questions
How many Watts are in 1 Calorie per Second?
1 Calorie per Second (cal/s) equals exactly 4.1868 Watts (W).
Why are there two kinds of horsepower?
Mechanical horsepower (550 ft·lb/s, about 745.7 W) was defined in Britain by James Watt in the 1780s, while metric horsepower (PS, about 735.5 W) was defined later in continental Europe using kilograms and meters instead of pounds and feet. Both describe roughly "the power of a horse," but because they were defined with different unit systems the two figures differ by about 1.4%.
How many watts is 1 horsepower?
1 mechanical horsepower equals exactly 745.6998715823 watts (about 745.7 W), while 1 metric horsepower (PS) equals exactly 735.49875 watts (about 735.5 W). Both are close to but not the same as 1 kilowatt (1,000 W).
How accurate are these conversions?
Every conversion factor used here is the exact, internationally recognized value (e.g. 1 hp = exactly 745.6998715823 W, 1 PS = exactly 735.49875 W) — results are limited only by floating-point display precision, not by rounded conversion constants.