Why is 1 watt equal to 1 joule per second?

Power is defined as the rate of energy transfer. One watt equals one joule of energy transferred per second. Therefore, entering a value in watts is equivalent to entering that many joules per second.

How many watts is 1 mechanical horsepower?

1 mechanical (SAE) horsepower equals exactly 745.69987 W. This is derived from the original definition: 550 foot-pounds-force per second.

What is the difference between mechanical, electrical, and metric horsepower?

Mechanical hp (745.69987 W) is the SAE standard used in North American automotive ratings. Electrical hp (746 W) is used for electric motors and differs by only 0.04%. Metric hp, or PS/CV (735.49875 W), is defined as 75 kgf·m/s and is about 1.4% lower than mechanical hp. It is standard in European car specifications.

How do I convert kilowatts to horsepower?

Multiply your kilowatt value by 1000 to get watts, then enter that into this tool. For example, 100 kW = 100,000 W, which equals approximately 134.1 mechanical hp.

Is joules to horsepower a power or energy conversion?

Joules per second (W) to horsepower is a power conversion. If you have joules (energy) and want to convert to horsepower-hours or horsepower-seconds, that is an energy conversion requiring a time component — use the Horsepower to Joules tool instead.

What is 1,000 watts in horsepower?

1,000 W equals approximately 1.3410 mechanical hp, 1.3405 electrical hp, and 1.3596 metric hp (PS).

Joules to Horsepower Calculator

Enter power in joules per second (or watts) and get the equivalent in mechanical, electrical, and metric (PS) horsepower instantly.

Power Input

Input Unit

Power in Joules per second (J/s)

Conversion Constants

1 hp (mechanical) = 745.69987 W
1 hp (electrical) = 746.00000 W
1 hp (metric, PS) = 735.49875 W

1 W = 1 J/s (joule per second)

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Summary

This calculator converts power measured in watts (joules per second, J/s) to horsepower. One watt equals one joule per second, so the conversion is a direct division by the watt-equivalent of each horsepower variant. The tool supports three standards: mechanical horsepower (745.69987 W, used in North American automotive ratings), electrical horsepower (746 W, used for electric motors), and metric horsepower — also called PS or CV (735.499 W, common in European specifications).

How it works

Enter the power value in joules per second (or watts) in the input field.
Results for all three horsepower variants update instantly.
Mechanical hp divides your watt value by 745.69987 W.
Electrical hp divides your watt value by 746 W.
Metric hp (PS/CV) divides your watt value by 735.49875 W.
Click any result row to copy the value to your clipboard.

Use cases

Convert electric motor or generator ratings from watts to horsepower.
Check engine power specs listed in kW against the hp equivalent.
Compare mechanical and metric horsepower for European vs. North American ratings.
Quickly translate solar panel or wind turbine output to horsepower.
Solve engineering homework problems involving SI and imperial power units.
Verify hydraulic pump or compressor power ratings across unit systems.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu