How Many Watts in 1 Horsepower? Exact Answer

One horsepower equals exactly 745.69987158227022 watts, usually rounded to 746 watts for everyday calculations. This page has a converter that takes any horsepower value (mechanical) and returns the equivalent in watts, plus the reverse if you need it. You enter the power in horsepower or watts, and the calculator gives you the other unit instantly.

Formula

The conversion is a simple multiplication or division:

Watts = Horsepower × 745.69987158227022

Horsepower = Watts ÷ 745.69987158227022

Where:

• Watts (W) – the SI unit of power, equal to one joule per second.
• Horsepower (hp) – the mechanical horsepower unit, defined as 550 foot-pounds per second.

The exact value comes from the definition: 1 hp = 550 ft·lbf/s. Converting that to metric gives 745.69987158227022 W. For most practical purposes, using 746 W is accurate to about 0.04%.

Worked Example

Using the default values from the calculator above:

1. Input: 1 horsepower
2. Formula: watts = 1 × 745.69987158227022
3. Calculation: 1 × 745.69987158227022 = 745.69987158227022
4. Rounded to 2 decimals: 745.70 watts

So 1 horsepower equals 745.70 watts when rounded to two decimal places. The calculator shows this as the headline answer.

Why Are There Different Horsepower Values?

Horsepower is not a single universal unit. The most common type is mechanical horsepower (the one used in this calculator), which is exactly 745.69987158227022 W. But you may encounter others:

• Metric horsepower (PS or cv) – used in Europe for car engines. 1 PS = 735.49875 W. It’s about 1.4% smaller than mechanical hp.
• Electrical horsepower – used for electric motors. 1 hp = 746 W exactly (a rounded value).
• Boiler horsepower – a much larger unit (about 9,809.5 W) used in the steam boiler industry.
• Hydraulic horsepower – used for pumps, based on flow and pressure.

When someone says “horsepowerâ€� without a qualifier, they almost always mean mechanical horsepower. That’s the standard in the US and UK for engines, motors, and machinery.

Where Horsepower Is Still Used

Watts are the official SI unit and are used everywhere in science and engineering. But horsepower persists in several everyday contexts:

• Car and motorcycle engines – vehicle power is nearly always quoted in hp (or PS in Europe).
• Electric motors – small motors (like those in appliances) are often rated in horsepower, even though they are electric.
• Air conditioning and heating – some HVAC equipment uses “tonâ€� (which is related to horsepower) or hp.
• Lawn mowers, generators, and power tools – these often list hp on the box.

Understanding the watt equivalent helps you compare devices that use different units. For example, a 2 hp motor uses about 1,491 W, which tells you its electrical consumption (before efficiency losses).

How to Convert Horsepower to Watts in Real Life

You don’t need to memorize the exact decimal. Here are practical methods:

1. Use 746 W per hp for quick mental math. For a 5 hp motor: 5 × 746 = 3,730 W (or 3.73 kW).
2. Use the calculator above for precise values, especially when dealing with fractional hp like 0.25 or 1.5.
3. For metric horsepower (PS), multiply by 735.5 instead of 746.

If you’re converting watts to horsepower, divide by 746. For example, a 1,500 W space heater is about 2.01 hp.

Common Mistakes and Misconceptions

Several errors trip people up when converting between these units:

• Using the wrong horsepower type – mixing mechanical hp and metric PS changes the result by ~1.4%, which matters in engineering but not for general estimates.
• Confusing power with energy – horsepower and watts measure power (rate of energy use). Energy is measured in watt-hours or joules. A 1 hp motor running for 1 hour uses 0.746 kWh, not 746 kWh.
• Rounding too early – if you round 745.7 to 700, you’ll be off by 6%. Use 746 for accuracy.
• Forgetting efficiency – an electric motor’s input power is higher than its output horsepower because of losses. A 1 hp motor might draw 1,200 W from the wall, not 746 W.

The last point is crucial: the 746 W figure is the mechanical output power. The electrical input is always higher.

Why 550 Foot-Pounds per Second?

The original definition of horsepower came from James Watt (the same man the watt is named after) in the late 18th century. He wanted a way to sell his steam engines to mine owners who used horses. He estimated that a strong horse could lift 550 pounds one foot in one second, and he defined that as one horsepower. The exact value has been standardized since, but the 550 ft·lbf/s definition remains.

That translates to 745.69987158227022 watts because one foot-pound is 1.3558179483314004 joules, and 550 × that equals the watt value. This historical origin is why the number is so odd – it’s based on a horse’s capability, not a clean metric number.

Frequently Asked Questions

Is 1 horsepower equal to 746 watts exactly?

Not exactly. The precise value is 745.69987158227022 watts. The number 746 is a rounded approximation that’s accurate to about 0.04%, which is fine for most practical purposes. In electrical engineering, the “electrical horsepowerâ€� is defined as exactly 746 W, but that’s a different unit.

How many watts is 2 horsepower?

2 mechanical horsepower equals 2 × 745.69987158227022 = 1,491.3997431645404 watts, or about 1,491 W. Using the rounded 746, you get 1,492 W – a negligible difference.

Why do car engines use horsepower instead of watts?

Tradition and marketing. Car buyers are familiar with horsepower, and the numbers are larger (e.g., 200 hp vs 149,140 W). In many countries, kW is also listed, especially in Europe. The unit doesn’t change the actual power, just the number.

How do I convert kilowatts to horsepower?

Divide kilowatts by 0.74569987158227022 (or multiply by 1.34102). For example, 100 kW ÷ 0.7457 = 134.1 hp. Conversely, 100 hp × 0.7457 = 74.57 kW.

Does 1 horsepower equal 1 horse?

No. The unit was based on a horse’s sustained output, but a real horse can briefly produce much more – up to 15 hp in a short burst. The figure represents a sustainable average, not a peak. Also, different horses vary in strength.

What is the difference between brake horsepower and horsepower?

Brake horsepower (bhp) is the power measured at the engine’s output shaft before losses from the gearbox, alternator, and other accessories. It’s essentially the same as mechanical horsepower. The term “brakeâ€� comes from the dynamometer (a brake) used to measure it. In practice, bhp and hp are used interchangeably for engines.

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in hp | Horsepower (mechanical) | hp | 1 | 0
in w | Watts | W | 745.7 | 0
out watts | Watts | W | hp * 745.69987158227022 | 2
out hp_out | Horsepower | hp | w / 745.69987158227022 | 4