Power Converter

Convert power between watts, kilowatts, megawatts, metric and imperial horsepower, BTU per hour and calories per second.

Open in the full calculator → — with every other tool, the AI tutor and PNG export.

How it converts

Result = value × (factor of the unit you convert from) ÷ (factor of the unit you convert to), every factor being the size of the unit in W:
1 kW = 1000 W
1 MW = 1 × 10⁶ W
1 HP (metric) = 735.499 W
1 HP (imperial) = 745.7 W
1 BTU/hr = 0.29307 W
1 cal/s = 4.184 W

Worked example

1 HP (imperial) = 1 × 745.7 ÷ 1 = 745.7 W.

Quick reference

1 W = 0.001 kW = 1 × 10^-6 MW = 0.00136 HP (metric) = 0.00134 HP (imperial) = 3.41214 BTU/hr = 0.23901 cal/s
1 HP (imperial) = 745.7 W = 0.7457 kW = 7.456999 × 10^-4 MW = 1.01387 HP (metric) = 2544.43 BTU/hr = 178.227 cal/s

From the Knowledge Base

Question: A 4 Ω resistor is connected across a 12 V battery. Find the current and the power dissipated.

Current: I = V / R = 12 / 4 = 3 A

Power, using P = VI: P = (12)(3) = 36 W

Check with the other two forms:
P = I²R = (3)²(4) = (9)(4) = 36 W ✔
P = V²/R = (12)² / 4 = 144 / 4 = 36 W ✔

All three agree, as they must. In an exam, doing one and checking with a second costs about ten seconds and catches most arithmetic slips.

Quoted from Ohm's Law and Electrical Power — V, I, R and P Connected.

Learn the method

About this converter

One of the unit converters in the Chemistry Calculator Suite, alongside its chemistry, physics and maths tools. Nothing is behind a login and no value you type is sent anywhere — the conversion runs in your own browser.

The Power converter above is the live tool — it converts right here on the page. The link under it opens the full suite with this set already selected.

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