A horsepower and torque calculator helps you understand the relationship between engine power, torque, and RPM. Whether you are comparing engine specs, converting between metric and imperial units, or evaluating power-to-weight ratio, this tool gives you instant results with the standard formula: HP = (Torque x RPM) / 5252.
HP / Torque / RPM Calculator
Enter any two values to calculate the third. Select which value to solve for.
Calculated value
Horsepower Converter
Torque Converter
Power-to-Weight Ratio
HP vs Torque Curve
This visualization shows the relationship between horsepower and torque across RPM for a given peak torque value. HP and torque always cross at 5252 RPM.
Common Engine Power & Torque Reference
| Engine Type | HP | Torque (lb-ft) | kW | Nm |
|---|---|---|---|---|
| Small 4-cyl economy | 130 | 118 | 97 | 160 |
| 4-cyl turbo sedan | 250 | 270 | 186 | 366 |
| V6 midsize | 300 | 270 | 224 | 366 |
| V8 truck / SUV | 400 | 410 | 298 | 556 |
| V8 performance | 460 | 420 | 343 | 569 |
| Supercharged V8 | 650 | 650 | 485 | 881 |
| Turbo diesel truck | 400 | 1000 | 298 | 1356 |
| EV motor (typical) | 350 | 390 | 261 | 529 |
Values shown are approximate and represent typical ranges for each engine category. Actual specifications vary by vehicle.
How to Use the Horsepower & Torque Calculator
Understanding the relationship between horsepower, torque, and RPM is fundamental to evaluating engine performance. Whether you are comparing vehicles, planning an engine build, or converting between metric and imperial power units, this horsepower torque calculator gives you quick, accurate results without any signup or downloads.
Step 1: Choose What to Solve For
The main calculator at the top lets you find any one of three values: horsepower, torque, or RPM. Click the button for the value you want to calculate. The corresponding input field becomes the output, and the other two become inputs. For example, if you know your engine makes 350 lb-ft of torque at 5500 RPM, select "Solve for HP" and enter those two values to find the horsepower.
Step 2: Enter Your Known Values
Type the two known values into their respective fields and click "Calculate." The formula used is HP = (Torque x RPM) / 5252, which is rearranged depending on what you are solving for. The constant 5252 comes from the definition of one mechanical horsepower, which equals 33,000 foot-pounds per minute divided by 2 times pi.
Step 3: Convert Between Power Units
Use the horsepower converter panel to switch between HP (mechanical), kilowatts (kW), PS (metric horsepower), and BTU per hour. This is useful when comparing engine specs from different countries. European manufacturers typically list power in kW or PS, while American specs use HP. One HP equals 0.7457 kW and 1.0139 PS.
Step 4: Convert Between Torque Units
The torque converter panel lets you convert between pound-feet (lb-ft), Newton-meters (Nm), and kilogram-meters (kg-m). This is especially helpful when looking at specifications from different regions. One lb-ft equals 1.3558 Nm, so a 400 Nm engine produces about 295 lb-ft of torque.
Step 5: Evaluate Power-to-Weight Ratio
Enter your vehicle's horsepower and curb weight to see the power-to-weight ratio in HP per ton, HP per pound, and pounds per HP. A higher HP-per-ton number means better acceleration potential. Typical economy cars have around 60-80 HP per ton, while performance vehicles range from 200 to over 400 HP per ton.
Understanding the HP vs Torque Curve
The curve visualization shows how horsepower and torque relate across the RPM range. For a given constant torque, horsepower increases linearly with RPM. The two curves always intersect at exactly 5252 RPM because the formula simplifies to HP = Torque at that point. In real engines, torque is not constant but peaks at a specific RPM and falls off at higher speeds, which is why the actual power curve peaks later than the torque curve. The reference table at the bottom provides typical engine specs for quick comparisons.
Frequently Asked Questions
Is this HP torque calculator really free?
Yes, this horsepower and torque calculator is completely free with no signup required. All calculations run locally in your browser and no data is ever sent to a server.
Is my data safe when using this tool?
Absolutely. Everything is calculated in your browser using JavaScript. No engine data or personal information is transmitted or stored anywhere. Your privacy is fully protected.
What is the formula for HP from torque and RPM?
The formula is HP = (Torque in lb-ft x RPM) / 5252. The constant 5252 comes from the relationship between the units: it equals 33,000 ft-lb/min (one horsepower) divided by 2 x pi. This means HP and torque always cross at exactly 5252 RPM.
What is the difference between HP and kW?
Horsepower (HP) is the imperial unit of power commonly used in the US, while kilowatts (kW) is the metric SI unit. One mechanical horsepower equals 0.7457 kilowatts. European vehicles often list power in kW or PS (metric horsepower) instead of HP.
What is the difference between lb-ft and Nm torque?
Pound-feet (lb-ft) is the imperial torque unit used primarily in the US, while Newton-meters (Nm) is the metric unit used in most other countries. One lb-ft equals 1.3558 Nm. When comparing engine specs from different regions, converting between these units is essential.
Why do HP and torque always cross at 5252 RPM?
This happens because of the formula HP = (Torque x RPM) / 5252. When RPM equals 5252, the equation simplifies to HP = Torque. The number 5252 is derived from the definition of one horsepower (33,000 ft-lb per minute) divided by 2 x pi.
What is PS (metric horsepower)?
PS stands for Pferdestarke, the German word for horsepower. It is the metric horsepower unit used in Europe, Japan, and many other countries. One mechanical HP equals 1.0139 PS, so the values are very close but not identical. A car rated at 300 PS has about 296 HP.
How does power-to-weight ratio affect performance?
Power-to-weight ratio measures how much horsepower is available per unit of vehicle weight. A higher ratio means faster acceleration. For example, a lightweight sports car with 300 HP will accelerate much faster than a heavy truck with the same power because it has more HP per ton.