Convert Calories to Horsepower-Hours
Convert Calories (cal) to Horsepower-Hours (hp·h) instantly and accurately.
Conversion Formula
hp·h = cal × 1.558565673e-6
About Calories
A calorie (cal) - the thermochemical calorie - is exactly 4.184 J, defined as the heat to raise 1 g of water by 1°C. Standard since 1954. The calorie is the fundamental unit of heat measurement in thermochemistry: glucose combustion releases 669.9 kcal/mol; water vaporisation requires 539.7 cal/g. Bond dissociation energies in quantum chemistry are often quoted in kcal/mol. Note: the dietary Calorie (capital C) on food labels is 1 kcal = 4,184 J - a factor-of-1,000 difference that causes persistent confusion. 1 cal = 4.184 J = 1.163 × 10⁻³ Wh.
About Horsepower-Hours
A horsepower-hour (hp·h) is the energy from one mechanical horsepower (745.6999 W) for one hour - exactly 2,684,519.54 J ≈ 2.685 MJ. James Watt coined the horsepower to compare his steam engines with mine horses; billing in hp·h preceded the kilowatt-hour tariff. The metric horsepower (PS = 75 kgf·m/s = 735.499 W) gives a slightly smaller metric-hp·h = 2,647,795 J, used in European and Japanese engine datasheets. Today the hp·h appears in marine engineering logs, mining energy accounting, and vintage industrial equipment. 1 hp·h = 2.6845 MJ = 0.74570 kWh = 641.19 kcal.
Quick Reference Table
| Calories (cal) | Horsepower-Hours (hp·h) |
|---|---|
| 1 cal | 1.559 × 10-6 hp·h |
| 2 cal | 3.117 × 10-6 hp·h |
| 5 cal | 7.793 × 10-6 hp·h |
| 10 cal | 1.559 × 10-5 hp·h |
| 25 cal | 3.896 × 10-5 hp·h |
| 50 cal | 7.793 × 10-5 hp·h |
| 100 cal | 0.000155857 hp·h |