HP to Watts: Convert Horsepower to Watts Without Guessing the Motor Size

CodexFuse Team · 2026-10-30T19:20:27.612Z · 9 min read min read

Convert hp to watts correctly: 1 hp is 745.7 watts, plus efficiency, with a worked workshop example and a free converter.

Converting hp to watts is how you turn a motor rating on a nameplate into a number you can actually plan around: how much power it draws, what circuit it needs, and what it will cost to run. One mechanical horsepower equals 745.7 watts, so a 2 hp motor delivers about 1,491 watts of mechanical power — but the electricity it pulls from the wall is higher, because no motor is 100% efficient.

This guide explains the conversion properly, works through a real workshop example end to end, and shows where the usual shortcuts go wrong. You can also skip the maths and use the free HP to Watts converter on CodexFuse, which gives watts plus kW, BTU/hr and PS equivalents instantly.

What is hp to watts conversion?

HP to watts conversion is the calculation that turns horsepower, a unit of mechanical power, into watts, the standard unit of electrical power. One mechanical horsepower is defined as 745.7 watts, one metric horsepower is 735.5 watts, and one electrical horsepower is 746 watts, so the exact answer depends on which horsepower your equipment uses.

That distinction matters more than most people expect. A pump, compressor or saw rated in metric horsepower will convert to a slightly lower watt figure than the same number in mechanical horsepower, and mixing the two up is enough to undersize a circuit or misjudge a generator.

The three horsepower definitions you will meet

Why does getting hp to watts wrong cost you money?

Getting hp to watts wrong costs you money because an understated watt figure leads to tripped breakers, an undersized generator or inverter, and a running-cost estimate that is too low. Overstating it has the opposite cost: you pay for a larger circuit, inverter or generator than the load ever needs.

The hidden trap is efficiency. Horsepower on a motor plate is usually output power — the mechanical work the shaft delivers. The electrical input is output divided by efficiency, so a 2 hp motor at 85% efficiency draws around 1,755 watts, not 1,491 watts. Leave efficiency out and your energy bill estimate will be roughly 15% light.

• Undersized supply: a circuit or generator sized on output watts alone can trip under load, especially at startup when motors briefly draw far more current.
• Wrong running cost: input watts, multiplied by hours run, is what the meter charges for — output watts alone understates the bill.
• Bad comparisons: two motors with the same hp rating can draw different input watts if their efficiencies differ.

Worked example: a 2 hp compressor in a small workshop

Consider a fictional scenario. Sara runs a small furniture workshop with a 2 hp air compressor. The nameplate says 2 hp mechanical, 85% efficiency, and she runs it about 6 hours a day, 26 days a month. She wants to know what it draws and what it costs to run, before she adds a second machine to the same circuit.

First, convert output power: 2 × 745.7 = 1,491 watts of mechanical output. Next, allow for efficiency to get input power: 1,491 ÷ 0.85 = 1,754 watts, or about 1.75 kW. Then work out monthly energy: 1.754 kW × 6 hours × 26 days = 273.6 kWh per month.

The lesson is practical: sizing on 1,491 watts would leave Sara about 263 watts short per machine, before startup surge. With the input figure, she can check breaker, cable and budget against numbers that match the meter. See also the energy converter guide.

How do you use the CodexFuse hp to watts tool?

You use the CodexFuse hp to watts tool by entering the horsepower value, reading the watt result, and checking the equivalents it shows alongside it. The tool page itself keeps the flow to three steps: enter HP, see watts, and get equivalents in kW, BTU/hr and PS.

1. Enter HP: type the horsepower figure from the nameplate into the tool at HP to Watts.
2. See watts: read the converted watt figure immediately, without installing anything or signing up for a calculation.
3. Get equivalents: use the kW, BTU/hr and PS figures shown to compare the motor with heaters, generators and specifications written in other units.

Which horsepower definition should you use?

Use mechanical horsepower (745.7 watts) for most US-rated motors and engines, metric horsepower (735.5 watts) for motors rated in PS or CV, and electrical horsepower (746 watts) when the nameplate explicitly gives an electrical rating. When in doubt, use the figure printed on the nameplate and note which definition it follows.

Common mistakes when converting hp to watts

Most hp to watts errors come from four habits, and all four are easy to fix once you know to look for them.

• Ignoring efficiency: output watts are not input watts. Divide by efficiency to get what the meter sees.
• Mixing hp definitions: mechanical, metric and electrical horsepower differ by up to 10 watts per hp, which adds up on larger motors.
• Forgetting startup surge: running watts size the energy bill; startup current sizes the breaker and generator.
• Confusing hp with torque: horsepower is power over time. A high-torque, low-speed motor and a low-torque, high-speed motor can share a hp rating and behave very differently.

For a related conversion that trips people up in the same way, the amps to watts guide shows how current ratings turn into real power numbers, including where voltage fits in. And if you need to turn running hours into a schedule or a cost window, the hours calculator guide covers that arithmetic cleanly.

What a hp to watts converter does not do

A hp to watts converter does not tell you whether a motor suits your job, what breaker size you need, or how long a generator will run under load. It converts a power rating; it does not measure your actual motor, check your wiring, or account for altitude, temperature or duty cycle.

Use the converter for arithmetic, then confirm electrical decisions with the nameplate and manufacturer data sheet.

Putting the rest of your business on one managed platform

Here is where the workshop analogy carries over to the business behind it. Sara's compressor problem was really a systems problem: one number, trusted without checking, quietly drove every downstream decision. The same thing happens when a business runs hosting on one provider, email on another, security on a third and backups nowhere in particular — each tool looks fine alone, and nobody owns the whole picture.

CodexFuse is built for that pain: an all-in-one, fully managed IT platform on credits, pay-as-you-go, with no subscriptions and no lock-ins. Create an account, add credits, move hosting, business email and security onto the platform, and let the managed team handle updates, monitoring and backups.

Frequently Asked Questions

How many watts is 1 hp?

One mechanical horsepower is 745.7 watts, one metric horsepower is 735.5 watts, and one electrical horsepower is 746 watts. For most general conversions, 746 watts per hp is a reasonable rounded figure, but use 745.7 watts when precision matters.

How do I convert hp to watts?

Multiply horsepower by 745.7 for mechanical hp, or use the free HP to Watts tool and enter your hp value to get watts, kW, BTU/hr and PS at once. For input power, divide the result by the motor's efficiency as a decimal.

Is hp to watts the same as hp to kW?

Yes, with a decimal shift: divide watts by 1,000 to get kilowatts. So 2 hp is about 1,491 watts, or 1.49 kW of mechanical output. Input kW will be higher once efficiency is included.

Why is my motor's watt rating higher than hp × 745.7?

Because the watt rating usually reflects electrical input, while hp reflects mechanical output. Efficiency losses — typically 10% to 20% — mean the motor draws more watts than it delivers as shaft power.

Can I size a generator from hp to watts alone?

No. Running watts are only part of the answer; startup surge, power factor and the other loads on the generator all matter. Use the conversion as a starting point, then check the generator maker's sizing guidance for motor loads.

What is the difference between hp and PS?

PS is the metric horsepower unit, equal to 735.5 watts, while mechanical hp is 745.7 watts. The two are close but not identical, so convert both to watts before comparing motors rated in different units.

Convert first, then fix the system behind the number

Converting hp to watts takes seconds, and it is the difference between a circuit that holds, a generator that copes and a bill that makes sense. Enter your motor's hp, check which horsepower definition applies, divide by efficiency for input power, and confirm startup current before you buy or wire anything.

Then apply the same thinking to the business around the workshop. Move your hosting, business email and security to CodexFuse today: create your account, add credits, and let a fully managed, pay-as-you-go platform take over the server babysitting, so you can get back to the work that actually earns money.