Kilowatts to Calories Per Second (kW to cal/s)

1 kilowatt equals 239.0057361 calories per second (rounded).

How to convert kilowatts to calories per second

To convert kilowatts to calories per second, multiply the number of kilowatts by 239.0057361. The factor is rounded to 10 significant digits. To go the other way, multiply calories per second by 0.004184.

calories per second = kilowatts × 239.0057361

Example: 10 kilowatts = 2,390.057361 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

Kilowatt (kW)

Metric (SI)Current unit

1,000 watts. Used for the power of motors, cars and household appliances.

A kilowatt is simply the watt with the SI prefix kilo, meaning a thousand, attached. The watt was adopted into the SI in 1960 and is small next to machinery, since an incandescent night light uses about 4 W, so the thousand-watt multiple suits engines, electric motors, tools and heaters. For readers used to older units, one kilowatt is roughly 1.34 horsepower.

Small electric heaters with a single element can use about 1 kW, and a domestic electric kettle or microwave oven draws a similar amount. The average household in the United States uses about 1 kW of electric power over time. On a clear midday near the equator, a square meter of Earth's surface receives about 1 kW of sunlight. Do not confuse the kilowatt with the kilowatt-hour on an electricity bill: the first is a rate, the second is the energy used by running one kilowatt for an hour, which equals 3,600,000 watt-seconds.

1 kilowatt = 1,000 watts (exactly).

Sources: Wikipedia: Kilowatt; Wikipedia: Orders of magnitude (power); BIPM: SI prefixes

Calorie Per Second (cal/s)

ScientificTraditional unit (still used in some regions)

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

See all power units.