Power Converter

Convert between watts, kilowatts, horsepower and BTU/h.

Value

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Converted power

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How it works

A power converter restates a rate of energy transfer in a different unit, moving between watts, kilowatts and megawatts on the metric side and mechanical horsepower, metric horsepower (PS), BTU per hour and foot-pounds per second on the customary side. It reduces whatever you enter to watts, the SI base unit for power, and then scales out to the unit you want, so a single mechanism covers engine ratings, appliance loads, heating and cooling capacities and electrical demand alike. This matters because power turns up in wildly different units depending on the industry. Car and motorcycle engines are quoted in horsepower or PS; air conditioners and furnaces in BTU per hour; solar panels, motors and data-centre loads in watts and kilowatts. Comparing a heat pump rated in BTU/h against a heater rated in kilowatts, or a US car's horsepower against a European car's PS, is impossible until everything sits in one unit. The convert-through-watts method is used because every power unit has a fixed, defined ratio to the watt — one mechanical horsepower is about 745.7 W, one metric PS is about 735.5 W — so pivoting through that base keeps results exact and needs only one factor per unit. Engineers, mechanics, HVAC installers, electricians and buyers comparing specs all reach for a power converter whenever a rating lands in an unfamiliar unit.

Formula

Convert to watts via known factors, then to the target unit

The input is multiplied by its unit's fixed number of watts to express the value in watts, then divided by the target unit's watt value to finish the conversion. Because every power unit is defined as a constant number of watts, chaining through this single SI base is algebraically exact and lets the converter store just one factor per unit instead of a separate rule for each of the many possible unit pairings.

Source:International System of Units (SI) — NIST

We review all our tools from time to time to ensure accuracy.

Worked example

Value:100From:hpTo:kW

100 hp × 745.6999 W = 74,569.99 W ÷ 1000 ≈ 74.57 kW.

How to use this calculator

1
Enter your values
Enter value, from and to.
2
Adjust the options
Fine-tune any options to match your situation.
3
Read your result
Converted power updates instantly as you type — no button to press.

Frequently asked questions

How many watts are in one horsepower?

One mechanical horsepower equals about 745.7 watts, the figure used here for the imperial 'hp' unit. Metric horsepower, written PS or CV and common in Europe, is slightly smaller at about 735.5 watts. So a 100 hp engine is roughly 74.6 kilowatts, while 100 PS is about 73.5 kilowatts. The two horsepower definitions differ by around one and a half percent.

What is the difference between hp and PS?

Mechanical horsepower (hp) is defined as 550 foot-pounds per second, about 745.7 watts, and is standard in the United States. Metric horsepower (PS, from the German Pferdestärke) is defined as 75 kilogram-force metres per second, about 735.5 watts, and is standard across much of Europe and Asia. Because PS is smaller, the same engine shows a slightly higher number in PS than in hp.

How do I convert BTU/h to watts for an air conditioner?

Multiply the BTU per hour figure by about 0.293 to get watts. A 12,000 BTU/h air conditioner, often called 'one ton' of cooling, is therefore about 3,517 watts or 3.5 kilowatts of heat-moving capacity. To reverse it, divide watts by 0.293. This lets you compare a BTU-rated cooler directly against a kilowatt-rated heat pump on the same scale.

How many kilowatts is 100 horsepower?

About 74.6 kilowatts, using mechanical horsepower of 745.7 watts each. This pivots through watts: 100 hp becomes 74,570 watts, which is 74.57 kilowatts. If the figure were metric PS instead, 100 PS would be about 73.5 kilowatts. The converter carries the full factor, so the displayed answer is precise to the decimals shown rather than a rounded estimate.

Why convert power through watts?

The watt is the SI base unit for power, one joule of energy per second, so every other power unit has a fixed, exactly defined ratio to it. Using the watt as the pivot means the converter needs only one factor per unit rather than a separate rule for each pair, keeps every result exact, and matches the unit that physics and electrical engineering equations expect for calculations.