Diesel Engine Torque Calculator

• From power and RPM: T = P / ω, where ω = 2π·RPM/60.
• From BMEP and displacement: T = (BMEP·Vd)/(4π) for 4-stroke, or T = (BMEP·Vd)/(2π) for 2-stroke.
• From force and crank radius: T = F·r.

Net torque applies your loss percentage: T_net = T_gross · (1 − loss%/100).

1. Select a calculation method that matches your available measurements.
2. Enter values and choose units for each input field.
3. Optionally set a loss percentage to estimate net torque.
4. Press Calculate to view results above the form.
5. Use the download buttons to export the latest result.

Torque is the twisting force delivered at the crankshaft. It is measured in N·m or lb·ft and is what you feel as pulling power at low speed. Many road diesels peak between 1,500 and 2,500 RPM, where boost and fueling are strongest. Light commercial units often exceed 400 N·m. Peak torque often aligns with maximum cylinder filling.

Power depends on both torque and rotational speed. When power stays constant, torque rises as RPM drops. This calculator uses T = P/ω with ω = 2π·RPM/60. Entering 120 kW at 2,000 RPM gives a gross torque near 573 N·m before losses, while 1,500 RPM yields roughly 764 N·m.

Brake mean effective pressure links cylinder pressure to average torque. For a 4‑stroke engine, torque equals (BMEP × displacement)/(4π). Typical BMEP values are about 14–22 bar for modern turbo diesels, and higher for performance builds. Example: 18 bar and 3.0 L corresponds to about 430 N·m gross.

Loss percentage estimates the difference between ideal crank torque and delivered torque after drivetrain or accessory losses. Chassis dyno readings may need 10–20% correction, while a direct engine dyno may need 2–8%. Cooling fans, alternators, and hydraulic pumps add parasitic load. Use net torque for real-world predictions.

If you have measured tangential force at the crank pin, torque is simply F × r. A 6.5 kN force at a 45 mm radius produces about 293 N·m. This method is useful for validating sensor data or teaching how leverage changes with stroke length.

The tool reports net and gross torque in three units: N·m, lb·ft, and kgf·m. For quick checks, 1 N·m equals about 0.7376 lb·ft. Net values help compare against brochures, while gross values help diagnose aggressive loss assumptions.

Use the calculator to size clutches, estimate towing performance, or compare tuning stages. Pair torque with gear ratios to estimate wheel torque, then compare to tire traction limits. For engineering tasks, verify results against manufacturer curves, account for boost lag, and apply safety factors for temperature and altitude.

Which method should I choose?

Use Power and RPM if you have dyno power and engine speed. Use BMEP and Displacement when you know average pressure and total displacement. Use Force and Crank Radius for measured tangential force at a known radius.

What does loss percentage mean?

It reduces gross torque to estimate net torque after drivetrain and accessory losses. If you measured wheel power, a higher loss value can approximate crank torque. If you measured crank power directly, keep losses low.

Why do I see higher torque at lower RPM?

For the same power, torque rises as RPM falls because ω is smaller. Real engines do not hold constant power everywhere, so use the RPM range where your power value applies.

Is BMEP valid for diesel engines?

Yes. BMEP is widely used to compare engine loading across sizes. It summarizes average pressure that would produce the measured brake work. Use the correct 4‑stroke or 2‑stroke option for best accuracy.

How accurate are the unit conversions?

They use standard factors: 1 N·m = 0.7376 lb·ft and 1 N·m = 0.1020 kgf·m. Minor rounding differences may appear, but they are negligible for typical engineering estimates.

Can I export results after refreshing the page?

Exports use the most recent calculated result saved in your session. If you refresh or open a new browser session before calculating again, export may be unavailable. Run one calculation first, then download CSV or PDF.