Convert Joules to Horsepower-Hours
Convert Joules (J) to Horsepower-Hours (hp·h) instantly and accurately.
Conversion Formula
hp·h = J × 3.725061360e-7
About Joules
The joule (J) is the SI unit of energy, defined as one newton acting through one metre (1 J = 1 N·m = 1 kg·m²/s²). Named after James Prescott Joule, whose 1840s paddle-wheel experiments established the mechanical equivalent of heat (~4.15 J = 1 calorie). One joule is modest: it lifts a 100 g apple by 1 m, heats 0.239 mL of water by 1°C, or powers a 1 W LED for 1 second. Daily adult resting metabolism is ~6-9 MJ. 1 J = 1 W·s = 0.23901 cal = 9.4782 × 10⁻⁴ BTU = 2.7778 × 10⁻⁷ kWh.
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
| Joules (J) | Horsepower-Hours (hp·h) |
|---|---|
| 1 J | 3.725 × 10-7 hp·h |
| 2 J | 7.45 × 10-7 hp·h |
| 5 J | 1.863 × 10-6 hp·h |
| 10 J | 3.725 × 10-6 hp·h |
| 25 J | 9.313 × 10-6 hp·h |
| 50 J | 1.863 × 10-5 hp·h |
| 100 J | 3.725 × 10-5 hp·h |