Engine Torque Curve Calculator

The relationship between an engine's power, torque, and RPM follows a fixed mathematical formula — and the Engine Torque Curve Calculator works that relationship in both directions. Select your calculation mode (torque from power & speed, or power from torque & speed), then enter your horsepower, engine speed (RPM), and torque values along with your idle RPM, peak torque RPM, and redline RPM to get your calculated torque or power, plus peak torque, peak power, and the torque-to-power ratio across the full RPM range.

Calculation Mode *

HP
RPM
lb-ft
RPM
RPM
RPM

Results

Calculated Torque

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Calculated Power

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Peak Torque

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Peak Power

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Torque/Power Ratio

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Results Table

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Frequently Asked Questions

How is torque calculated from horsepower and RPM?

Torque is calculated using the formula: Torque = (Horsepower × 5,252) ÷ RPM. This conversion factor 5,252 comes from the relationship between foot-pounds, horsepower, and rotational speed in the imperial system.

What is the difference between torque and horsepower?

Torque measures the rotational force an engine produces, while horsepower measures the rate at which work is done. Torque determines acceleration feel, while horsepower determines top speed capability.

At what RPM should peak torque occur?

Peak torque typically occurs between 2,500-4,500 RPM in most engines. Lower RPM peak torque provides better low-end pulling power, while higher RPM peak torque favors high-speed performance.

How do I interpret a torque curve graph?

The torque curve shows how much rotational force your engine produces across its RPM range. A flat, broad curve indicates good drivability, while a peaked curve suggests the engine is optimized for a specific RPM range.

Why does horsepower continue rising after peak torque?

Horsepower is torque multiplied by RPM, so even as torque decreases at higher RPM, horsepower can still increase until the torque drop-off becomes too steep. This typically happens at much higher RPM than peak torque.

What factors affect an engine's torque curve shape?

Factors include engine displacement, compression ratio, camshaft profile, intake and exhaust design, turbocharging/supercharging, and fuel delivery system. Each component influences where and how much torque is produced.

How accurate are calculated torque curves compared to dyno testing?

Calculated curves provide good estimates but actual dyno testing is more accurate. Real engines have variations due to individual tolerances, tuning, condition, and environmental factors that calculations cannot account for.