Horsepower to Calories Per Second (hp to cal/s)
1 horsepower equals 178.2265467 calories per second (rounded).
How to convert horsepower to calories per second
To convert horsepower to calories per second, multiply the number of horsepower by 178.2265467. The factor is rounded to 10 significant digits. To go the other way, multiply calories per second by 0.005610836423 (rounded).
calories per second = horsepower × 178.2265467
Example: 10 horsepower = 1,782.265467 calories per second.
Several different horsepower units exist. This site lists mechanical (745.7 W), metric (735.5 W) and electrical (746 W) horsepower separately.
About these units
Horsepower (hp)
The mechanical horsepower: 550 foot-pounds per second, about 745.7 watts. James Watt coined it to compare steam engines with draft horses.
Horsepower was a sales pitch before it was a unit. Late in the 18th century the Scottish engineer James Watt adopted the term to compare the output of steam engines with the draft horses they replaced. His 1782 experiments found that a brewery horse could produce 32,400 foot-pounds-force per minute, and in 1783 he and Matthew Boulton standardized the figure at 33,000 foot-pounds-force per minute. Customers could then be told how many horses an engine would replace.
That figure works out to 550 foot-pounds-force per second, or about 745.7 watts: the power needed to lift 550 pounds by one foot in one second. Several cousins exist, including metric horsepower and electrical horsepower, defined as exactly 746 W. Car ratings added more confusion. Early British taxable horsepower was a formula based on bore and cylinder count, not measured output, and American ratings before 1972 used SAE gross brake horsepower, measured without accessories. In the European Union, horsepower may be used only as a supplementary unit under Directive 80/181/EEC, in force from 1 January 2010.
1 horsepower = 745.6998716 watts (approximately).
Sources: Wikipedia: Horsepower; Wikipedia: Metric horsepower
Calorie Per Second (cal/s)
Exactly 4.184 watts.
Pairing the small calorie with the second yields a unit that fits laboratory work, where heat flows are modest and timed in seconds. With the thermochemical calorie, defined as exactly 4.184 joules, one calorie per second is exactly 4.184 watts. NIST lists the thermochemical calorie per second at 4.184 watts as an exact factor, and the same list gives the kilocalorie per second as 4,184 watts.
The 15 degree calorie is a little different at about 4.1855 joules, and the International Table calorie of 1956 is 4.1868 joules, so a rate quoted in calories per second without a qualifier can differ by a few parts in ten thousand. The calorie itself is regarded as obsolete since the joule became the official SI unit of energy in 1948, and the watt, one joule per second, has replaced this rate in current work.
1 calorie per second = 4.184 watts (exactly).
Sources: NIST SP 811, Appendix B.8; Wikipedia: Calorie
Related conversions
- Calories per second to horsepower (reverse)
- Horsepower to watts
- Horsepower to kilowatts
- Horsepower to megawatts
- Horsepower to gigawatts
- Horsepower to metric horsepower
- Horsepower to BTU per hour
- Horsepower to milliwatts
- Horsepower to electrical horsepower
- Horsepower to foot-pounds per second
- Horsepower to tons of refrigeration
- Horsepower to kilocalories per hour
- Horsepower to ergs per second
- Watts to calories per second
- Kilowatts to calories per second
See all power units.