Convert power between watts, kilowatts, megawatts, horsepower (mechanical and metric), BTU/h and ft-lb/s — with exact factors.
What Is a Power Converter?
A power converter translates the rate of doing work between units: 1 mechanical horsepower = 745.6999 W; 1 metric horsepower (PS) = 735.4988 W. James Watt defined the horsepower as 550 ft-lb/s from brewery horses; the metric world rounded it to 75 kg·m/s — hence the two definitions, about 1.4% apart. Car specs, motors and generators quote hp; electrical equipment quotes watts and kilowatts.
How to Use
- Enter the value.
- Pick the “from” unit — note mechanical vs metric hp.
- Pick the “to” unit.
- Click “Convert Power”.
Formula
Convert to watts first (value × from-factor), then divide by the to-factor.
Worked Example
1 hp (mechanical) → watts: 745.6999 W. And 1 kW → hp: 1,000 ÷ 745.699872 = 1.3410 hp.
How It Works, In Plain Words
Every unit on the dropdown is stored as its value in watts: a kilowatt is 1,000, a megawatt is 1,000,000, mechanical horsepower is 745.699872, metric PS is 735.49875, a BTU per hour is 0.29307107 and a foot-pound per second is 1.3558179482. The tool multiplies your value by the from-factor to reach watts, then divides by the to-factor — the worked example runs the second hop in reverse, turning 1 kW into horsepower with 1,000 ÷ 745.699872 = 1.3410 hp. Routing everything through watts means the seven units never need their own pairwise tables, and both directions use the same two numbers.
Horsepower is where the care is needed, because the dropdown holds two of them. Mechanical hp — the UK and US unit, James Watt’s 550 ft-lb/s — is 745.6999 W, while metric PS, the European figure rounded from 75 kg·m/s, is 735.4988 W; the introduction puts them about 1.4% apart. Results are shown to four decimal places, so 1 hp displays as 745.6999 W exactly as the worked example states, and small units like BTU per hour keep their precision instead of collapsing to zero.
Real-World Uses
A car buyer comparing a European brochure quoted in PS with a US review in mechanical hp converts both into watts — or directly across — and discovers how much of the gap is the 1.4% definition difference rather than a real difference in the engine. A homeowner sizing a generator or checking an appliance plate moves between the watts and kilowatts that electrical equipment quotes, the introduction’s pairing, without touching horsepower at all. An HVAC technician working with the BTU per hour figures heating and cooling equipment still uses converts a rating into kilowatts to compare it with the rest of the system. Each job starts from whichever unit the document in front of them happens to print. The converter supplies the common scale; the reader supplies the context.
Benefits
- Seven units including both horsepower definitions
- Exact defined factors
- Both directions in one tool
- Car, motor and generator friendly
Features of Our Tool
- Instant results in your browser
- No sign-up, no download, 100% free
- Works on mobile, tablet and desktop
- Clear step-by-step explanation below the tool
- Private — your entries never leave your device
Common Mistakes
- Mixing mechanical and metric horsepower — 1.4% apart, matters in specs
- Confusing power (kW) with energy (kWh)
- Using BTU/h as energy — it is power (energy per hour)
Common Mistakes to Avoid
The first mistake is mixing the two horsepowers: the list warns they sit 1.4% apart, which matters in specs — a figure in PS read as mechanical hp overstates the machine, because 735.4988 W is not 745.6999 W. The second is confusing power with energy: kilowatts measure the rate, kilowatt-hours the amount, and no conversion here turns one into the other. The third follows from it — treating BTU/h as energy, when the list spells out that it is power, energy per hour. And check the dropdown before trusting a result: with both horsepowers side by side, selecting the wrong one is the easiest error on the page. A moment spent on the unit labels saves a wrong specification.
FAQ
How many watts is 1 horsepower?
745.6999 W (mechanical); 735.4988 W (metric PS).
How many hp is 1 kW?
1.3410 hp (mechanical).
What is the difference between hp and PS?
Mechanical hp = 745.6999 W (UK/US); metric PS = 735.4988 W (Europe) — about 1.4% apart.
How many BTU/h is 1 kW?
About 3,412.14 BTU/h.
Is horsepower still used?
Yes — cars, boats, lawn equipment and HVAC still quote hp alongside kW.
Can I convert kilowatts to megawatts with this tool?
Yes — both are on the dropdown. A kilowatt is 1,000 watts and a megawatt is 1,000,000 watts in the tool’s factors, so the conversion is a straight pass through watts like every other pair.
Why are there two horsepower units?
Because the two traditions defined it differently: James Watt set mechanical hp at 550 ft-lb/s (745.6999 W), while the metric world rounded its version to 75 kg·m/s, giving PS at 735.4988 W — about 1.4% apart, as the introduction explains.