Watts to Kilocalories per Hour Converter

Convert between watts (W) and kilocalories per hour (kcal/h) instantly. Ideal for engineering, HVAC, and estimating calories burned from power output.

Watts to kcal/h

1 W = 0.859845 kcal/h
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kcal/h to Watts

1 kcal/h = 1.163 W (approx.)
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Quick presets

Click a common power level to see its equivalent in kilocalories per hour.

How to convert watts to kilocalories per hour

A watt (W) is the SI unit of power, equal to one joule per second. A kilocalorie per hour (kcal/h) is a power unit commonly used to express heat output or energy expenditure in nutrition and exercise.

The exact relationship is:

1 W = 0.8598452279 kcal/h
1 kcal/h = 1.163 W (approximately)

To convert from watts to kilocalories per hour:

\(\text{kcal/h} = \text{W} \times 0.859845\)

Example: 150 W to kcal/h

  1. Start with the power in watts: \(P = 150\ \text{W}\).
  2. Multiply by the conversion factor 0.859845:

\(\text{kcal/h} = 150 \times 0.859845 \approx 128.98\ \text{kcal/h}\)

So a continuous power output of 150 W corresponds to about 129 kcal/h.

How to convert kilocalories per hour to watts

To go the other way, divide by the same factor (or multiply by its reciprocal):

\(\text{W} = \dfrac{\text{kcal/h}}{0.859845} \approx \text{kcal/h} \times 1.163\)

Example: 300 kcal/h to watts

  1. Start with the power in kcal/h: \(P = 300\ \text{kcal/h}\).
  2. Convert to watts:

\(\text{W} = \dfrac{300}{0.859845} \approx 348.3\ \text{W}\)

So burning 300 kcal per hour corresponds to a mechanical/electrical power of about 348 W.

Where is W ↔ kcal/h conversion used?

  • Exercise & cycling: bike power meters show watts, while training plans and nutrition use kilocalories.
  • Metabolic studies: resting metabolic rate or energy expenditure can be expressed in kcal/h.
  • HVAC & heating: some specifications use kcal/h instead of watts or BTU/h.
  • Engineering: comparing heat losses or gains to electrical power consumption.

Table: common watt values in kcal/h

Watts (W) kcal/h (approx.)
50 W 43.0 kcal/h
75 W 64.5 kcal/h
100 W 86.0 kcal/h
150 W 129.0 kcal/h
200 W 172.0 kcal/h
250 W 215.0 kcal/h
300 W 258.0 kcal/h

From power to calories burned per hour

If you know your average power output in watts during an activity, you can estimate the mechanical energy per hour in kilocalories using this converter. However, the human body is not 100% efficient.

Typical cycling efficiency is around 20–25%. That means for every 1 kcal of mechanical work, your body may expend 4–5 kcal of metabolic energy.

Rough rule of thumb:

\(\text{Metabolic kcal/h} \approx \dfrac{\text{Mechanical kcal/h}}{\text{Efficiency}}\)

Example: 200 W → 172 kcal/h mechanical. At 22% efficiency, metabolic kcal/h ≈ 172 / 0.22 ≈ 782 kcal/h.

FAQ

How accurate is the conversion factor?

The factor 0.8598452279 is based on the exact definitions:

  • 1 watt = 1 joule per second
  • 1 kilocalorie = 4184 joules

Combining these gives:

\(1\ \text{W} = \dfrac{3600\ \text{J/h}}{4184\ \text{J/kcal}} = 0.8598452279\ \text{kcal/h}\)

Is “kcal” the same as “Calorie” on food labels?

Yes. In nutrition, an uppercase “Calorie” (Cal) is defined as one kilocalorie (kcal). So 100 Cal on a label is 100 kcal.