How is this calculated?
HP = (torque lb-ft * RPM) / 5252 kW = HP * 0.7457 PS = HP * 1.01387 Drag-strip HP = ((weight lb / ET)^3) * 0.00272 Trap-speed HP = weight lb * (MPH / 234)^3 Metric weight entries are converted to pounds before drag-strip formulas run.
Example: 350 lb-ft at 5,200 RPM equals 346.5 HP. A 3,800 lb car trapping 112 MPH estimates about 417 HP by the Hale trap-speed formula.
How do I use this calculator?
- Choose the unit or currency setting that matches your vehicle data.
- Enter the required vehicle, route, fuel, weight or loan values in the calculator form.
- Review inline warnings and correct any missing or negative inputs.
- Read the live result card for the primary answer and supporting totals.
- Use the worked example if you want to check the formula with sample values.
- Copy, share or print the results for comparison or record keeping.
What do the terms mean?
- Horsepower
- A unit of power equal to 550 ft-lb per second.
- Torque
- Rotational force, commonly measured in lb-ft or Nm.
- kW
- Kilowatt, the SI unit of power.
- PS
- Metric horsepower, slightly larger than mechanical horsepower.
- Trap speed
- Vehicle speed at the end of a quarter-mile pass.
What are real-world examples?
| Scenario | Inputs | Result | Notes |
|---|---|---|---|
| Street V8 | 350 lb-ft at 5,200 RPM | 346 HP | 258 kW |
| Diesel truck | 900 lb-ft at 1,800 RPM | 308 HP | 230 kW |
| Sport compact | 260 lb-ft at 6,000 RPM | 297 HP | 221 kW |
| Drag estimate | 3,600 lb, 11.8 sec | 306 HP | ET formula |
What tips improve accuracy?
- Use wheel horsepower for chassis dyno comparisons and engine horsepower for engine dyno claims.
- Torque and horsepower cross numerically at 5,252 RPM when using lb-ft.
- Drag-strip formulas are estimates and depend on traction, aero and gearing.
- Corrected dyno numbers account for weather conditions.
- Diesel engines often make peak torque at lower RPM than gasoline engines.
- For electric motors, use kW when manufacturer data is provided that way.
Did you know? EPA estimates commonly use 8.89 kg CO2 per gallon of gasoline and 10.18 kg CO2 per gallon of diesel for tailpipe carbon dioxide calculations.
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Frequently asked questions
Is this calculator free to use?
Yes. The calculator runs in your browser, does not require an account and can be printed or copied for your records.
Can I use this for official tax, loan or compliance filing?
Use it as an estimate. For official filing, financing or enforcement decisions, verify the final numbers with your lender, tax authority, manufacturer rating label or compliance professional.
Why are my real-world results different?
Real vehicles vary with load, speed, terrain, temperature, tire condition, maintenance, driver behavior and measurement quality.
Does the calculator save my units?
Yes. Unit and currency selections that are marked as preferences are stored in localStorage on your device so the next visit starts with your preferred setting.
Can I share the result?
Yes. Use the Share button if your browser supports native sharing, or copy the permalink and result summary.
Does it work on mobile?
Yes. The layout stacks on small screens, keeps labels visible and recalculates as you type.
How accurate are the formulas?
The formulas are standard industry math for estimates. Accuracy depends on the input values and whether the assumptions match your vehicle and jurisdiction.
When was this page updated?
This page was last updated on 2026-05-01 for 2026 planning assumptions and source links.