Power Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
To convert power, it's brought back to a common unit (the watt) then converted into the new unit. For example, 100 metric horsepower represents about 73.55 kilowatts.
Explanation
The watt (W) is the SI unit of power, but several historical units remain widely used depending on the field: metric horsepower (ch, from the French 'cheval-vapeur'), a traditional metric unit still used in France for car engine power, equals exactly 735.49875 W (defined as 75 kilogram-force-meters per second). Imperial horsepower (hp), used in the United States and the United Kingdom, is a different unit equal to 745.699872 W — a gap of about 1.4% from metric horsepower, often ignored in quick comparisons but significant for high power values. BTU per hour (BTU/h) is still used in the United States for the thermal power of air conditioners and heaters. Converting power amounts to multiplying the value by the factor that brings it back to watts, then dividing by the target unit's factor — exactly what this calculator does. A European car spec sheet expressed 'in horsepower' almost always uses metric horsepower (ch), while an American spec sheet in 'hp' uses imperial horsepower: the two numeric values therefore aren't directly comparable without conversion. For the electrical power consumed by an appliance and its cost, see our electricity consumption calculator; for electrical power itself (P = U × I), our electrical power calculator.
Example: converting 100 metric horsepower to kilowatts
Inputs
Value: 100. Starting unit: metric horsepower (ch). Target unit: kilowatts.
Calculation
100 ch = 100 × 735.49875 = 73,549.875 W. In kilowatts: 73,549.875 ÷ 1000 ≈ 73.55 kW.
Result
100 metric horsepower represents about 73.55 kilowatts.
Frequently asked questions
Are metric horsepower (ch) and imperial horsepower (hp) the same unit?
No, they're two distinct historical units, although often confused in everyday language: metric horsepower (ch, 735.49875 W) is used in France and most European countries, while imperial horsepower (hp, 745.699872 W) is used in the United States and the United Kingdom. The gap between the two, about 1.4%, is small but real: 100 ch equals about 98.6 hp, not exactly 100 hp.
Why is BTU/h still used for American air conditioners?
Because the United States traditionally uses the imperial system for most household thermal and energy measurements, including the cooling or heating power of appliances. In Europe, the same quantity is generally expressed directly in watts or kilowatts.
Which engine power unit gives the higher numeric value for the same physical power?
Since the watt is the reference unit, a value in metric or imperial horsepower is always numerically smaller than the same power expressed in watts (since 1 ch or 1 hp represents several hundred watts). Between ch and hp themselves, for the same real physical power, the value in ch is slightly higher than in hp (since metric horsepower represents a slightly lower power than imperial horsepower).