From
To
Learn more about
Watts to horsepower: exact catalog factor, conversion chart, and motor nameplate tips
Conversion formula
Verification: factors follow standard unit definitions; round for display only.
Quick reference chart
| Watt | Horsepower |
|---|---|
| 1 | 0.001341 |
| 2 | 0.002682 |
| 3 | 0.004023 |
| 4 | 0.005364 |
| 5 | 0.006705 |
| 6 | 0.008046 |
Educational explanation
Watts to horsepower
Convert W to hp when an appliance label, solar inverter spec, or LED driver lists watts but a US motor chart, automotive brochure, or pump curve quotes mechanical horsepower.
Watts (W) and mechanical horsepower (hp) both measure power. On this site, horsepower is anchored to the watt via the shared power catalog: 1 hp = 745.699871582 W exactly. Therefore:
hp = W ÷ 745.699871582 · equivalently hp = W × 0.0013410220895955138
That constant traces to 550 ft·lbf per second expressed in SI units. For shop-floor estimates, W ÷ 746 is close; use the full catalog value for documents that must match this converter.
Step-by-step conversion (worked example — 5,500 W motor)
A pool pump nameplate lists 5,500 W input:
- hp = 5,500 ÷ 745.699871582 = 7.375621 hp
- Round for display: ~7.37 hp on a comparison sheet
Second worked example (745.7 W anchor)
Sanity-check 745.699871582 W (one catalog horsepower in watts):
- 745.699871582 ÷ 745.699871582 = 1 hp exactly
Third worked example (11,200 W EV charger)
A 240 V × 48 A circuit delivers up to 11,520 W (ideal resistive):
- 11,520 ÷ 745.699871582 = 15.4486 hp
- Marketing may still quote kW—compare like units before sizing a generator in hp.
Quick mental estimate
Divide watts by 746 for mechanical hp. Example: 3,730 W → 3,730 ÷ 746 ≈ 5 hp (exact: 5.002 hp). The shortcut is within about 0.05% of the site factor.
Watt to horsepower conversion chart
| Watts (W) | Horsepower (hp) | Typical context |
|---|---|---|
| 745.700 W | 1 hp | Definition anchor (catalog) |
| 373 W | 0.5 hp | Fractional motor class (approx.) |
| 746 W | 1 hp (rounded) | Rule-of-thumb reference |
| 1,500 W | 2.012 hp | Space heater, microwave |
| 3,730 W | 5.002 hp | ~5 hp motor class |
| 5,500 W | 7.376 hp | Pool pump, light industrial |
| 7,457 W | 10.000 hp | ~10 hp motor class |
| 74,570 W | 100.00 hp | ~100 hp industrial motor |
Where W → hp comes up
- Motors & pumps: Nameplates increasingly list W or kW; legacy charts stay in hp.
- Automotive: European kW specs vs US hp ratings—convert before comparing peak power.
- Generators: Inverter specs in W; portable gasoline units marketed in hp.
Horsepower to watts
Convert hp to W when a motor plate or vehicle spec lists horsepower but your breaker calculation, solar string sizing, or heat-pump comparison uses watts.
Multiply horsepower by 745.699871582 to obtain watts on this site.
W = hp × 745.699871582
Step-by-step conversion (worked example)
Convert 5 hp shop motor to watts:
- 5 × 745.699871582 = 3728.499 W
- ≈ 3.73 kW for a utility demand letter
Horsepower to watt conversion chart
| Horsepower (hp) | Watts (W) | Typical context |
|---|---|---|
| 1 hp | 745.700 W | Catalog anchor |
| 3 hp | 2237.1 W | Pool pump, bench grinder |
| 5 hp | 3728.5 W | Shop motor |
| 10 hp | 7457 W | Light industrial fan |
| 100 hp | 74570 W | Process compressor class |
Mechanical vs metric hp, kW, and related converters
This hp is mechanical (745.699871582 W). Metric horsepower (PS) differs slightly—confirm the source before comparing car specs.
Power units compared
| Unit | Watts (this site) | Notes |
|---|---|---|
| 1 hp (mechanical) | 745.699871582 W | Catalog Horsepower entry |
| 1 kW | 1,000 W | SI prefix—exact |
| 1 hp | 0.745700 kW (rounded) | kW = W ÷ 1000 after hp→W |
Common mistakes
- Using 750 W per hp—close for mental math, not catalog-exact.
- Confusing hp with kW on the same line item without converting.
- Ignoring power factor when converting electrical VA to mechanical hp output.
Related converters
See kW to hp, watt to kilowatt, kW to hp, and kilowatt to megawatt.
Frequently asked questions
How many watts are in one horsepower?
1 hp = 745.699871582 W on this site (mechanical horsepower from the shared power catalog).
What is the formula watts to horsepower?
hp = W ÷ 745.699871582.
What is the formula horsepower to watts?
W = hp × 745.699871582.
How do I convert 5500 W to hp?
5500 ÷ 745.699871582 ≈ 7.376 hp.
Is dividing by 746 accurate?
746 is a common rounded inverse. The catalog uses 745.699871582 W per hp—about 0.04% difference at the 1 hp anchor.
What is metric horsepower (PS)?
Metric hp is about 735.5 W—different from mechanical hp here. Confirm which hp a vehicle brochure uses before converting.
How do watts relate to kilowatts?
1 kW = 1000 W exactly. Convert W→kW first if your report uses SI kilowatts instead of hp.
Can I round-trip W and hp?
Yes—W→hp→W should recover the original within floating-point tolerance using the same catalog constant.
Does electrical horsepower equal mechanical horsepower?
The conversion factor is the same power-unit definition. Real motor shaft output is lower than electrical input because of efficiency and power factor—separate those steps from unit conversion.
Popular conversions