Watt to Horsepower Converter
Convert watts to horsepower with our free online power converter.
Quick Answer
1 Watt = 0.001341 horsepower
Formula: Watt × conversion factor = Horsepower
Use the calculator below for instant, accurate conversions.
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All conversion formulas on UnitsConverter.io have been verified against NIST (National Institute of Standards and Technology) guidelines and international SI standards. Our calculations are accurate to 10 decimal places for standard conversions and use arbitrary precision arithmetic for astronomical units.
Watt to Horsepower Calculator
How to Use the Watt to Horsepower Calculator:
- Enter the value you want to convert in the 'From' field (Watt).
- The converted value in Horsepower will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Power category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Watt to Horsepower: Step-by-Step Guide
Converting Watt to Horsepower involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
hp = W × 0.00134102Example Calculation:
1 W = 0.001341 hp
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
Not for professional use. Results should be verified before use in any critical application. View our Terms of Service for more information.
Need to convert to other power units?
View all Power conversions →What is a Watt and a Horsepower?
The Physics of Power
Power is the rate at which work is done or energy is transferred.
Mathematical Definition: $$ P = \frac{E}{t} $$ Where:
- $P$ = Power (Watts)
- $E$ = Energy (Joules)
- $t$ = Time (seconds)
Dimensional Analysis: $$ 1 \text{ W} = 1 \frac{\text{J}}{\text{s}} = 1 \frac{\text{kg} \cdot \text{m}^2}{\text{s}^3} $$
Electrical Definition: For electrical circuits, power is the product of voltage and current: $$ P = V \times I $$ Where:
- $P$ = Power (Watts)
- $V$ = Voltage (Volts)
- $I$ = Current (Amperes)
Example:
- A device drawing 5 Amps at 120 Volts consumes:
- $P = 120 \text{ V} \times 5 \text{ A} = 600 \text{ W}$
Watt vs. Watt-Hour (The Confusion)
This is the #1 source of confusion about watts.
- Watt (W): A unit of power (rate of energy use).
- Watt-hour (Wh) or Kilowatt-hour (kWh): A unit of energy (total amount of energy used).
The Analogy:
- Watts are like miles per hour (speed).
- Watt-hours are like miles (distance).
Example:
- A 100 W light bulb running for 10 hours uses:
- $100 \text{ W} \times 10 \text{ h} = 1,000 \text{ Wh} = 1 \text{ kWh}$
Your electricity bill charges you for kWh (energy), not kW (power).
The Original Experiment
James Watt didn't just guess. He observed horses working in coal mines, lifting coal up a shaft using a pulley system.
- A horse could pull with a force of 180 pounds.
- It walked in a circle with a 24-foot diameter (approx 75.4 ft circumference).
- It completed the circle about 2.5 times per minute.
$$ \text{Work} = \text{Force} \times \text{Distance} $$ $$ \text{Power} = \frac{\text{Work}}{\text{Time}} $$
$$ 180 \text{ lbs} \times (24 \text{ ft} \times \pi \times 2.5) \approx 32,572 \frac{\text{ft}\cdot\text{lb}}{\text{min}} $$
Watt rounded this up to 33,000 ft⋅lb/min to be safe. Dividing by 60 seconds gives the classic definition: 1 hp = 550 ft⋅lb/s
Types of Horsepower
The world couldn't agree on just one "horsepower," so we have several:
1. Mechanical Horsepower (Imperial)
- Symbol: hp, hp(I)
- Value: 745.69987158227022 Watts
- Definition: 550 ft⋅lb/s
- Where used: USA, UK, Commonwealth countries. This is what you see on a Ford Mustang spec sheet.
2. Metric Horsepower (Pferdestärke)
- Symbol: PS, cv, ch, pk, ks
- Value: 735.49875 Watts
- Definition: The power to lift 75 kg by 1 meter in 1 second.
- $75 \text{ kg} \times 9.80665 \text{ m/s}^2 \times 1 \text{ m/s} = 735.5 \text{ W}$
- Where used: Europe, Asia, South America.
- German: Pferdestärke (PS)
- French: Cheval-vapeur (ch)
- Italian: Cavallo vapore (cv)
- Difference: Metric hp is about 1.4% smaller than Imperial hp. A 500 hp car is 507 PS.
3. Electrical Horsepower
- Symbol: hp(E)
- Value: 746 Watts (Exactly)
- Definition: Used for rating electric motors to simplify calculations.
4. Boiler Horsepower
- Symbol: bhp
- Value: 9,809.5 Watts (~13.1 mechanical hp)
- Definition: The power required to evaporate 34.5 lbs of water into steam in one hour at 212°F.
- Where used: Industrial steam boilers and power plants. Warning: Do not confuse this with Brake Horsepower (bhp)!
5. Hydraulic Horsepower
- Definition: Power available within a hydraulic system.
- Formula: $\text{hp} = \frac{\text{Pressure (psi)} \times \text{Flow (gpm)}}{1714}$
- Where used: Heavy machinery, drilling rigs.
Note: The Watt is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Horsepower belongs to the imperial/US customary system.
History of the Watt and Horsepower
: James Watt and the Steam Revolution
The Man Behind the Unit
James Watt (1736-1819) was a Scottish instrument maker and inventor. While he didn't invent the steam engine, he made it vastly more efficient, enabling the Industrial Revolution.
His Key Innovation (1769): Watt added a separate condenser to the Newcomen steam engine. This kept the main cylinder hot, reducing fuel consumption by 75%. Suddenly, steam engines became economical for factories, mines, and transportation.
The Irony: Watt also coined the term "horsepower" to market his engines (see our horsepower article). Yet the unit named after him—the watt—would eventually replace horsepower as the global standard for electrical power.
Official Adoption
- 1882: The British Association for the Advancement of Science officially adopted the "watt" as the unit of electrical power, replacing the awkward "volt-ampere."
- 1889: The International Electrical Congress endorsed the watt.
- 1960: The watt was incorporated into the International System of Units (SI) as the standard unit of power.
The Original Definition
The watt was originally defined in relation to the absolute watt, based on mechanical power: $$ 1 \text{ W} = 10^7 \text{ erg/s} $$ (The erg is an obsolete CGS unit of energy.)
Today, the watt is defined in terms of fundamental SI units: $$ 1 \text{ W} = 1 \frac{\text{kg} \cdot \text{m}^2}{\text{s}^3} $$
: The Marketing Genius of James Watt
The term "horsepower" is arguably the most successful marketing slogan in engineering history.
The Problem: In the late 1700s, the Industrial Revolution was just starting. Mines were flooded with water, and owners used teams of horses to drive pumps. James Watt had invented a vastly superior steam engine, but he had a hard time explaining how much better it was. Saying "it produces 20,000 foot-pounds per minute" meant nothing to a mine boss.
The Solution: Watt spoke their language. He calculated what one of their horses could do, then rated his engine in "horses." "This engine will replace 10 of your horses." Suddenly, the value proposition was clear. The mine owner could calculate the cost of feeding and housing 10 horses versus buying one engine.
The Irony: Watt actually overestimated the power of a horse.
- A typical horse can sustain about 0.7 hp for a full day.
- Watt's "1 hp" (33,000 ft-lb/min) is actually a grueling pace that a horse can only maintain for a few hours.
- By defining the unit as stronger than a real horse, Watt ensured his customers were never disappointed. If they bought a "5 hp" engine, it would easily outwork 5 real horses.
Common Uses and Applications: watts vs horsepower
Explore the typical applications for both Watt (imperial/US) and Horsepower (imperial/US) to understand their common contexts.
Common Uses for watts
1. Electrical Appliances
Every electrical device has a power rating in watts, indicating how much electricity it consumes when operating.
- Low Power (1-100 W): LED bulbs, phone chargers, alarm clocks.
- Medium Power (100-1,000 W): Laptops, TVs, fans, blenders.
- High Power (1,000-5,000 W): Microwaves, hair dryers, space heaters, ovens.
- Very High Power (5,000+ W): Electric water heaters, EV chargers, central AC.
2. Electricity Bills
Your utility company charges you for energy (kWh), not power (kW).
- Formula: $\text{Cost} = \text{Power (kW)} \times \text{Time (hours)} \times \text{Rate ($/kWh)}$
- Example: A 1,500 W space heater running 8 hours/day for 30 days:
- Energy = $1.5 \text{ kW} \times 8 \text{ h/day} \times 30 \text{ days} = 360 \text{ kWh}$
- Cost = $360 \text{ kWh} \times $0.10/\text{kWh} = $36$
3. Solar Panels & Renewable Energy
Solar panels are rated by their peak power output in watts under ideal conditions (full sun, 25°C).
- Residential Panel: 300-400 W.
- 10-Panel System: 3,000-4,000 W (3-4 kW).
- Daily Energy (sunny location): ~15-20 kWh.
4. Electric Vehicles
EV charging power determines how fast the battery charges.
- Level 1 (120V outlet): 1,400 W (1.4 kW) - adds ~4 miles/hour.
- Level 2 (240V charger): 7,200 W (7.2 kW) - adds ~25 miles/hour.
- DC Fast Charging: 50,000-350,000 W (50-350 kW) - adds 150-1,000 miles/hour.
5. Audio Equipment
Speaker and amplifier power ratings indicate maximum output.
- Bluetooth Speaker: 5-20 W.
- Home Theater Receiver: 100-200 W per channel.
- Concert PA System: 10,000-50,000 W.
When to Use horsepower
1. Automotive Industry
This is the domain of the horsepower. Despite the world moving to metric (kW), car enthusiasts and manufacturers in the US, UK, and even Europe still heavily market "HP" or "PS."
- BHP (Brake Horsepower): The power measured at the engine's crankshaft (before losses in the transmission). This is the number in the brochure.
- WHP (Wheel Horsepower): The power that actually reaches the tires. Usually 15-20% less than BHP due to friction in the gears and axles.
2. Aviation
- Piston Engines: Small planes (Cessna 172) are rated in hp (e.g., Lycoming O-320 is 160 hp).
- Turboprops: Often rated in Shaft Horsepower (shp).
- Jet Engines: Rated in Thrust (lbs or kN), not horsepower. However, you can calculate "equivalent horsepower" based on speed, though it varies wildly.
3. Home Appliances
- Garbage Disposal: 1/3 hp to 1 hp.
- Garage Door Opener: 1/2 hp to 1.25 hp.
- Blender: "2 Peak HP" (Marketing term—usually means the motor would produce that right before it burns out).
- Air Conditioner: Historically rated in hp, now mostly BTU/h or Tons. (1 hp $\approx$ 9000 BTU/h in cooling capacity, roughly).
4. Electric Motors
Industrial motors are strictly rated in hp (US) or kW (Global).
- 1 hp motor: Runs a small conveyor or drill press.
- 10 hp motor: Runs a large industrial fan or compressor.
- 100+ hp motor: Runs municipal water pumps or rock crushers.
Additional Unit Information
About Watt (W)
How do I calculate my electricity bill from watts?
Step-by-Step:
- Find the power rating (in watts) on the device label.
- Estimate daily usage (in hours).
- Calculate daily energy: $\text{kWh/day} = \frac{\text{Watts} \times \text{Hours}}{1,000}$
- Calculate monthly energy: $\text{kWh/month} = \text{kWh/day} \times 30$
- Calculate cost: $\text{Cost} = \text{kWh/month} \times \text{Rate}$
Example: 1,500 W space heater, 6 hours/day, $0.12/kWh
- Daily energy: $(1,500 \times 6) / 1,000 = 9 \text{ kWh}$
- Monthly energy: $9 \times 30 = 270 \text{ kWh}$
- Monthly cost: $270 \times $0.12 = $32.40$
What is the difference between watts and volts?
- Volts (V): Electrical pressure (potential difference). Like water pressure in a pipe.
- Amps (A): Electrical flow rate (current). Like gallons per minute.
- Watts (W): Electrical power (rate of energy transfer). Like horsepower.
The Relationship: $$ \text{Watts} = \text{Volts} \times \text{Amps} $$
Example:
- A device at 120 V drawing 10 A consumes:
- $120 \times 10 = 1,200 \text{ W}$
Why do some devices say "VA" instead of "W"?
VA (Volt-Amperes) is apparent power, while W (Watts) is real power.
- For resistive loads (heaters, incandescent bulbs), VA = W.
- For reactive loads (motors, transformers), VA > W.
Example:
- A motor rated at 1,000 VA with a power factor of 0.8 actually consumes:
- $1,000 \times 0.8 = 800 \text{ W}$
How many watts does a house use?
Average US Home:
- Peak Power: 5,000-10,000 W (5-10 kW) when AC, oven, and dryer run simultaneously.
- Average Power: 1,000-1,500 W (1-1.5 kW) continuous.
- Monthly Energy: 900-1,000 kWh.
Off-Grid Solar System Sizing:
- To power a typical home, you'd need a 10-15 kW solar array with battery storage.
What is a megawatt?
1 Megawatt (MW) = 1,000,000 Watts = 1,000 kW
Used for large-scale power generation and consumption.
- Wind Turbine: 2-3 MW.
- Small Power Plant: 50-100 MW.
- Large Coal Plant: 500-1,000 MW.
- Nuclear Reactor: 1,000 MW (1 GW).
How many watts can a standard outlet provide?
US Standard (120V, 15A circuit): $$ 120 \text{ V} \times 15 \text{ A} = 1,800 \text{ W} $$ Safe continuous load: 1,440 W (80% of max).
US Heavy Duty (120V, 20A circuit): $$ 120 \text{ V} \times 20 \text{ A} = 2,400 \text{ W} $$ Safe continuous load: 1,920 W.
240V Outlet (Dryer, Oven, EV Charger): $$ 240 \text{ V} \times 30 \text{ A} = 7,200 \text{ W} $$
Can I run a 1,500 W heater on a 15A circuit?
Technically yes, but it's pushing the limit.
- 1,500 W at 120 V draws 12.5 A.
- Circuit Breaker: 15 A.
- Safety Margin: You should stay under 80% (12 A).
Recommendation: Run the heater alone on that circuit. Don't plug in other devices.
What is "peak watts" vs "continuous watts"?
- Continuous Watts: The power a device can sustain indefinitely.
- Peak Watts (Surge Watts): The power a device draws briefly during startup.
Example: Refrigerator
- Running: 150 W.
- Startup (Compressor Kick): 600-800 W for 1-2 seconds.
Why It Matters: When sizing a generator or inverter, you need to account for peak watts, not just continuous watts.
About Horsepower (hp)
Does a horse actually have 1 horsepower?
No!
- Sustained: A healthy horse can sustain exactly 1 hp (Watt's definition) for a few hours, or about 0.7 hp for a full work day.
- Peak: In a full gallop or jump, a horse can produce 14.9 hp.
- Human: A human can produce 1 hp for about 10-15 seconds (sprinting up stairs).
What is "Brake Horsepower" (bhp)?
Bhp is the power measured at the engine's output shaft using a device called a "brake" (dynamometer) to hold the engine speed steady. It measures the engine's raw power before it goes through the gearbox, alternator, power steering pump, and differential. Wheel Horsepower (whp) is what actually hits the road, which is usually 15% lower than bhp.
Why do electric cars have "Horsepower"?
Electric motors produce power (Watts). However, to make them comparable to gas cars for consumers, manufacturers convert the kW rating to hp.
- Tesla Model 3 Performance: 450 hp.
- Actually: ~340 kW. Electric horsepower is technically defined as exactly 746 W, but for marketing, the conversion 1 kW = 1.341 hp is used.
What is "Tax Horsepower" (CV)?
In countries like France (CV) and the UK (RAC hp), cars used to be taxed based on a formula involving cylinder bore diameter, not actual power.
- Citroën 2CV: Named "Deux Chevaux" (Two Horses).
- Actual Power: 9 hp (early models) to 29 hp.
- Tax Rating: 2 CV. This system led to engines with long strokes and small bores to cheat the taxman.
Can I convert Thrust to Horsepower?
Not directly. Thrust is force; Horsepower is power (force $\times$ speed).
- A jet engine at a standstill produces 0 hp (because distance moved is 0), but massive thrust.
- At 600 mph, that same thrust produces massive horsepower.
- Approx Formula: $\text{hp} = \frac{\text{Thrust (lbs)} \times \text{Speed (mph)}}{375}$
What is the most powerful machine ever built?
The Saturn V rocket.
-
First stage thrust: 7.6 million pounds.
-
Speed at burnout: 6,000 mph.
-
Peak Power: ~160,000,000 horsepower. That's equivalent to about 500,000 Corvettes taking off at once.
-
Dynamometer (Dyno): A device used to measure force, torque, and power.
-
Indicated Horsepower (ihp): Theoretical power calculated from gas pressure in the cylinders (ignoring friction).
-
Friction Horsepower (fhp): Power lost to friction within the engine. (ihp - bhp = fhp).
-
Shaft Horsepower (shp): Power delivered to a propeller shaft (ships/airplanes).
-
Specific Power: Power per unit of displacement (e.g., "100 hp per liter").
-
Power-to-Weight Ratio: Horsepower divided by vehicle weight. The #1 predictor of acceleration.
Conversion Table: Watt to Horsepower
| Watt (W) | Horsepower (hp) |
|---|---|
| 0.5 | 0.001 |
| 1 | 0.001 |
| 1.5 | 0.002 |
| 2 | 0.003 |
| 5 | 0.007 |
| 10 | 0.013 |
| 25 | 0.034 |
| 50 | 0.067 |
| 100 | 0.134 |
| 250 | 0.335 |
| 500 | 0.671 |
| 1,000 | 1.341 |
People Also Ask
How do I convert Watt to Horsepower?
To convert Watt to Horsepower, enter the value in Watt in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our power converter page to convert between other units in this category.
Learn more →What is the conversion factor from Watt to Horsepower?
The conversion factor depends on the specific relationship between Watt and Horsepower. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.
Can I convert Horsepower back to Watt?
Yes! You can easily convert Horsepower back to Watt by using the swap button (⇌) in the calculator above, or by visiting our Horsepower to Watt converter page. You can also explore other power conversions on our category page.
Learn more →What are common uses for Watt and Horsepower?
Watt and Horsepower are both standard units used in power measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our power converter for more conversion options.
For more power conversion questions, visit our FAQ page or explore our conversion guides.
Helpful Conversion Guides
Learn more about unit conversion with our comprehensive guides:
📚 How to Convert Units
Step-by-step guide to unit conversion with practical examples.
🔢 Conversion Formulas
Essential formulas for power and other conversions.
⚖️ Metric vs Imperial
Understand the differences between measurement systems.
⚠️ Common Mistakes
Learn about frequent errors and how to avoid them.
All Power Conversions
Other Power Units and Conversions
Explore other power units and their conversion options:
- Milliwatt (mW) • Watt to Milliwatt
- Kilowatt (kW) • Watt to Kilowatt
- Megawatt (MW) • Watt to Megawatt
- Gigawatt (GW) • Watt to Gigawatt
- Metric Horsepower (PS) • Watt to Metric Horsepower
- Electric Horsepower (hp(E)) • Watt to Electric Horsepower
- BTU per Hour (BTU/h) • Watt to BTU per Hour
- BTU per Minute (BTU/min) • Watt to BTU per Minute
- BTU per Second (BTU/s) • Watt to BTU per Second
- Foot-pound per Second (ft⋅lb/s) • Watt to Foot-pound per Second
Verified Against Authority Standards
All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.
National Institute of Standards and Technology — Fundamental physical constants and unit conversions
Bureau International des Poids et Mesures — International System of Units (SI) definitions and standards
International Organization for Standardization — Quantities and units international standards series
Last verified: February 19, 2026