How to Convert HP to Wattage [Horsepower to Watts]
ZacharyWilliamA complete guide to understanding, calculating, and applying HP to W conversions
1. Introduction
Horsepower (HP) and watts (W) are both measurements of power, but they are used in different contexts. Converting between the two is essential when comparing motors, engines, generators, or even portable power stations. In this guide, you’ll learn the exact formula, see real-world examples, and use our quick reference conversion table.
2. What is Horsepower?
The term “horsepower” was introduced by James Watt to compare steam engines to the pulling power of horses. Today, HP is used to describe the output of car engines, pumps, industrial machines, and electric motors.
- Mechanical HP: Common in the U.S. — 1 HP = 745.7 W
- Metric HP: Common in Europe — 1 HP = 735.5 W
- Electrical HP: Based on electric motor output
3. What is Wattage?
The watt (W) is the SI unit of power. It measures how much energy is used or produced per second. For electrical systems, the relationship is simple:
You’ll see watts on appliances, electronics, and portable power stations because it directly relates to energy consumption and capacity.
4. The Conversion Formula
The standard formula to convert horsepower to watts is:
For metric horsepower, use Watts = Horsepower × 735.5.
5. Step-by-Step Conversion Examples
Example 1: 2 HP Motor
2 HP × 745.7 = 1,491.4 W
Example 2: 5 HP Generator
5 HP × 745.7 = 3,728.5 W
Example 3: Reverse Conversion
1,500 W ÷ 745.7 ≈ 2.01 HP
6. Horsepower to Wattage Conversion
Different industries use different horsepower standards. Use the correct factor below to convert horsepower (HP) to watts (W) and kilowatts (kW). Unless otherwise noted, values are rounded to the nearest whole watt (kW to 2 decimals) for readability.
- Mechanical HP → W: 1 HP = 745.7 W (common in U.S. mechanical contexts)
- Electric HP → W: 1 HP = 746 W (electric motors / nameplate conversions)
- Metric HP (PS) → W: 1 HP = 735.5 W (common in Europe/automotive)
- Boiler HP → W: 1 HP = 9,809.5 W (steam/boiler rating; ≈ 9.81 kW)
Mechanical Horsepower to Watts
Formula: Watts = HP × 745.7
| Horsepower (HP) | Watts (W) | Kilowatts (kW) |
|---|---|---|
| 0.25 | 186 | 0.19 |
| 0.50 | 373 | 0.37 |
| 0.75 | 559 | 0.56 |
| 1.00 | 746 | 0.75 |
| 1.50 | 1,119 | 1.12 |
| 2.00 | 1,491 | 1.49 |
| 3.00 | 2,237 | 2.24 |
| 5.00 | 3,728 | 3.73 |
| 7.50 | 5,593 | 5.59 |
| 10.00 | 7,457 | 7.46 |
Electric Horsepower to Watts
Formula: Watts = HP × 746
| Horsepower (HP) | Watts (W) | Kilowatts (kW) |
|---|---|---|
| 0.25 | 186 | 0.19 |
| 0.50 | 373 | 0.37 |
| 0.75 | 560 | 0.56 |
| 1.00 | 746 | 0.75 |
| 1.50 | 1,119 | 1.12 |
| 2.00 | 1,492 | 1.49 |
| 3.00 | 2,238 | 2.24 |
| 5.00 | 3,730 | 3.73 |
| 7.50 | 5,595 | 5.60 |
| 10.00 | 7,460 | 7.46 |
Metric Horsepower to Watts
Formula: Watts = HP × 735.5
| Horsepower (HP) | Watts (W) | Kilowatts (kW) |
|---|---|---|
| 0.25 | 184 | 0.18 |
| 0.50 | 368 | 0.37 |
| 0.75 | 552 | 0.55 |
| 1.00 | 736 | 0.74 |
| 1.50 | 1,103 | 1.10 |
| 2.00 | 1,471 | 1.47 |
| 3.00 | 2,206 | 2.21 |
| 5.00 | 3,678 | 3.68 |
| 7.50 | 5,517 | 5.52 |
| 10.00 | 7,355 | 7.36 |
Boiler Horsepower to Watts
Formula: Watts = HP × 9,809.5 (1 boiler HP ≈ 33,475 BTU/h)
| Horsepower (HP) | Watts (W) | Kilowatts (kW) |
|---|---|---|
| 0.25 | 2,452 | 2.45 |
| 0.50 | 4,905 | 4.90 |
| 0.75 | 7,357 | 7.36 |
| 1.00 | 9,810 | 9.81 |
| 1.50 | 14,714 | 14.71 |
| 2.00 | 19,619 | 19.62 |
| 3.00 | 29,429 | 29.43 |
| 5.00 | 49,048 | 49.05 |
| 7.50 | 73,572 | 73.57 |
| 10.00 | 98,095 | 98.10 |
- Use mechanical or electric HP for motors/engines depending on the spec sheet convention.
- Use metric HP when comparing European automotive specs (often labeled PS).
- Use boiler HP only for steam/boiler capacity—it is not interchangeable with mechanical HP.
7. Wattage to Horsepower Conversion
To calculate horsepower (HP) from watts (W), divide by the correct factor depending on the standard used. Results below are rounded for readability.
- Mechanical: HP = Watts ÷ 745.7
- Electric: HP = Watts ÷ 746
- Metric: HP = Watts ÷ 735.5
- Boiler: HP = Watts ÷ 9,809.5
Mechanical Watts to Horsepower
Formula: HP = Watts ÷ 745.7
| Watts (W) | Horsepower (HP) | Kilowatts (kW) |
|---|---|---|
| 500 | 0.67 HP | 0.50 |
| 750 | 1.01 HP | 0.75 |
| 1,000 | 1.34 HP | 1.00 |
| 1,500 | 2.01 HP | 1.50 |
| 2,000 | 2.68 HP | 2.00 |
| 3,000 | 4.02 HP | 3.00 |
| 5,000 | 6.71 HP | 5.00 |
| 7,500 | 10.06 HP | 7.50 |
| 10,000 | 13.41 HP | 10.00 |
Electric Watts to Horsepower
Formula: HP = Watts ÷ 746
| Watts (W) | Horsepower (HP) | Kilowatts (kW) |
|---|---|---|
| 500 | 0.67 HP | 0.50 |
| 750 | 1.01 HP | 0.75 |
| 1,000 | 1.34 HP | 1.00 |
| 1,500 | 2.01 HP | 1.50 |
| 2,000 | 2.68 HP | 2.00 |
| 3,000 | 4.02 HP | 3.00 |
| 5,000 | 6.70 HP | 5.00 |
| 7,500 | 10.06 HP | 7.50 |
| 10,000 | 13.40 HP | 10.00 |
Metric Watts to Horsepower
Formula: HP = Watts ÷ 735.5
| Watts (W) | Horsepower (HP) | Kilowatts (kW) |
|---|---|---|
| 500 | 0.68 HP | 0.50 |
| 750 | 1.02 HP | 0.75 |
| 1,000 | 1.36 HP | 1.00 |
| 1,500 | 2.04 HP | 1.50 |
| 2,000 | 2.72 HP | 2.00 |
| 3,000 | 4.08 HP | 3.00 |
| 5,000 | 6.80 HP | 5.00 |
| 7,500 | 10.20 HP | 7.50 |
| 10,000 | 13.60 HP | 10.00 |
Boiler Watts to Horsepower
Formula: HP = Watts ÷ 9,809.5
| Watts (W) | Horsepower (HP) | Kilowatts (kW) |
|---|---|---|
| 5,000 | 0.51 HP | 5.00 |
| 10,000 | 1.02 HP | 10.00 |
| 20,000 | 2.04 HP | 20.00 |
| 30,000 | 3.06 HP | 30.00 |
| 40,000 | 4.08 HP | 40.00 |
| 50,000 | 5.10 HP | 50.00 |
| 75,000 | 7.65 HP | 75.00 |
| 100,000 | 10.20 HP | 100.00 |
| 150,000 | 15.29 HP | 150.00 |
| 200,000 | 20.39 HP | 200.00 |
- Use mechanical/electric formulas for motors and engines.
- Use metric HP when working with European car specs (often labeled PS).
- Use boiler HP strictly for steam/boiler capacity ratings.
8. Practical Applications
- Portable Power Stations: Know how much HP-rated equipment they can support.
- Cars & Engines: Compare performance in HP vs kW specs.
- Home DIY: Match your power tools to the right backup source.
9. Common Mistakes
- Mixing up mechanical HP (745.7 W) and metric HP (735.5 W).
- Ignoring efficiency losses: a 1 HP motor doesn’t always deliver a full 746 W.
- Confusing watts with kilowatts (1 kW = 1,000 W).
10. Tools & Calculators
You can use online HP to Watts calculators, but knowing the formula helps in quick estimates. If you’re sizing a generator or portable power station, converting HP to W ensures you won’t run out of capacity.
11. Conclusion
Converting HP to watts is simple once you remember the key formula: 1 HP ≈ 746 W. Whether you’re comparing engines, motors, or choosing a portable power solution, these conversions give you the clarity you need.
12. FAQs
How many watts is 1 HP exactly?
1 mechanical HP = 745.7 W. For metric horsepower, 1 HP = 735.5 W.
How many HP is a 2000 W motor?
2000 ÷ 745.7 ≈ 2.68 HP.
Why are there different types of horsepower?
Different standards exist: mechanical HP (U.S.), metric HP (Europe), and electrical HP (motors). Each is based on slightly different definitions of work per second.
Can I use this formula for electric car motors?
Yes, but efficiency and control electronics affect the real output. Always refer to the manufacturer’s data for accuracy.
What’s the difference between watts and kilowatts?
1 kilowatt (kW) = 1000 watts (W). For example, 2 HP ≈ 1.49 kW.
How do I convert watts back to horsepower?
Use the formula: HP = Watts ÷ 745.7 (mechanical HP). Example: 1500 W ÷ 745.7 ≈ 2.01 HP.
Is horsepower still used in modern equipment?
Yes. Horsepower is common in cars, lawnmowers, and industrial machines, while watts or kilowatts are more common in electrical devices and global standards.
Do efficiency losses matter in conversion?
Yes. A 1 HP motor may not deliver the full 745.7 W of usable output due to energy lost as heat or friction. Always factor in efficiency (often 80–95%).
How do I size a portable power station using HP?
First, convert the motor’s HP rating to watts. Then check that your power station can handle both the running watts and surge watts. For example, a 2 HP pump (~1492 W) needs a station with at least 2000 W surge capacity.
Which is more reliable for comparing engines: HP or kW?
Kilowatts (kW) are the standard SI unit, making global comparisons easier. Horsepower is still popular in automotive marketing, but kW is more precise and universal.
What’s the difference between brake horsepower (BHP) and HP?
BHP is measured at the engine’s output shaft without drivetrain losses, while general HP can include other conditions. BHP is often closer to real-world usable power.
UDPOWER S1200 Portable Power Station
With 1190Wh capacity and 1200W rated output, the S1200 covers home backup, outdoor work, and camping essentials—perfectly aligned with your HP↔W calculations.
* Pricing and availability may vary by bundle and region.
