Kilocalories to Horsepower-hours (kcal to hp⋅h)

1 kilocalorie equals 0.001558565673 horsepower-hours (rounded).

1 kilocalorie = 0.001558565673 horsepower-hours

How to convert kilocalories to horsepower-hours

To convert kilocalories to horsepower-hours, multiply the number of kilocalories by 0.001558565673. The factor is rounded to 10 significant digits. To go the other way, multiply horsepower-hours by 641.6155683 (rounded).

horsepower-hours = kilocalories × 0.001558565673

Example: 10 kilocalories = 0.01558565673 horsepower-hours.

The 'calorie' on food labels is really a kilocalorie. The thermochemical calorie (4.184 J) is used here unless marked IT.

About these units

Kilocalorie (kcal)

ScientificTraditional unit (still used in some regions)

1,000 thermochemical calories (4,184 J). The 'Calorie' on food labels in North America.

Marcellin Berthelot separated the gram calorie from the kilogram calorie in 1879, and the American chemist Wilbur Atwater adopted a capital-C Calorie for the large unit in 1887 in a widely read article on the energy in food. Joseph Howard Raymond proposed the term kilocalorie in his 1894 textbook. The two names now describe the same quantity, 1,000 small calories, which at the thermochemical value is 4,184 J or 4.184 kJ.

Food labels carry the unit today, though practice differs by region. North American labels use kilocalories almost exclusively, European labels show kilojoules and kilocalories together under EU Regulation 1169/2011, and Chinese labels give kilojoules only. Typical energy contents are about 9 kcal per gram for fat, about 4 for carbohydrate and protein, and about 7 for alcohol. In electrical terms, 4,184 J works out to about 1.162 watt-hours, since one watt-hour is 3,600 J. NIST also lists a kilocalorie based on the International Table calorie, which is 4,186.8 J.

1 kilocalorie = 4,184 joules (exactly).

Sources: Wikipedia: Calorie (includes kilocalorie); NIST SP 811, Appendix B.8 (energy conversion factors)

Horsepower-hour (hp⋅h)

US & ImperialTraditional unit (still used in some regions)

About 2.685 MJ (0.7457 kWh), the energy of one mechanical horsepower for an hour.

Multiplying a power by a time gives energy, and this unit does it with James Watt's horse. In the late 18th century Watt compared steam engines with the draft horses they replaced. After an experiment in 1782 that suggested a brewery horse delivered 32,400 foot-pounds per minute, he and Matthew Boulton rounded the figure to 33,000 foot-pounds per minute the next year. One mechanical horsepower is therefore about 745.7 W, and sustaining it for an hour gives roughly 2.685 MJ, or 0.7457 kWh.

The unit is now outdated and outside the SI. Railways still use it to settle accounts when locomotives are lent between companies. In one example, a 2,500 hp unit used for 12 hours is owed back as 30,000 hp-hours, repayable with a 3,000 hp unit for 10. A German variant, the Pferdestaerkenstunde, uses the metric horsepower of about 735.5 W and equals 2,647.7955 kJ, so one hp-hour is about 1.014 PSh.

1 horsepower-hour = 2,684,519.538 joules (approximately).

Sources: Wikipedia: Horsepower-hour; Wikipedia: Horsepower; Wikipedia: Conversion of units of energy

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