RPM to Torque Calculator - Calculator Academy

Reviewed By: Patrick Myers (BSME)

Enter the total power (HP) and the rotational speed (RPM) into the calculator to determine the Torque From RPM.

Torque From RPM Formula

The following formula is used to calculate the Torque From RPM.

T = 5252.08 * P / S

Where T is the Torque From RPM (lb-ft)
P is the total power (HP)
S is the rotational speed (RPM)

To calculate the torque from RPM, multiply the the horsepower by 5252.08, then divide the rotational speed.

RPM to Torque Conversion Table at 1 HP (T(lb-ft) = 5252.08 × HP ÷ RPM)
Rotational Speed (RPM)	Torque (lb-ft)
500	10.504
750	7.003
1,000	5.252
1,200	4.377
1,500	3.501
1,800	2.918
2,000	2.626
2,500	2.101
3,000	1.751
3,600	1.459
4,000	1.313
4,500	1.167
5,000	1.050
5,252	1.000
5,500	0.955
6,000	0.875
6,500	0.808
7,000	0.750
7,500	0.700
8,000	0.657
* Rounded to 3 decimals. Assumes constant power of 1 HP. To scale for other power levels, multiply torque values by your HP. 1 lb-ft ≈ 1.35582 Nm.

How to Calculate Torque From RPM?

The following two example problems outline how to calculate the Torque From RPM.

Example Problem #1:

First, determine the total power (HP). In this example, the total power (HP) is measured to be 500.
Next, determine the rotational speed (RPM). For this problem, the rotational speed (RPM) is calculated to be 1000.
Finally, calculate the Torque From RPM using the formula above:

T = 5252.08 * P / S

Inserting the values from above and solving the equation with the imputed values gives:

T = 5252.08 * 500 / 1000 = 2626.04 (lb-ft)

Example Problem #2:

Using the same process as example problem 1, we first define the variables outlined by the formula. In this case, the values are:

total power (HP) = 600

rotational speed (RPM) = 2000

Entering these values into the formula or calculator above gives us::

T = 5252.08 * 600 / 2000 = 1575.62 (lb-ft)

Follow-Up Calculations

If your engine makes 250 hp at 4,000 rpm, this calculator shows about 328 lb-ft of torque before drivetrain losses. From there, the next useful step is to translate torque into wheel force, because a 3.20 first gear with a 3.73 axle multiplies that engine output into well over 3,900 lb-ft at the tires.

A result of 300 lb-ft at 5,252 rpm is the same as 300 hp, which is why torque and horsepower are so closely tied together. You can estimate top speed from power to see how that output might translate into highway performance, since aerodynamics can keep a strong engine from gaining much more speed even when torque stays high.

If this calculator gives you 350 lb-ft at 5,252 rpm, that corresponds to about 350 hp, and in a 3,500 lb car that becomes roughly 200 hp per ton. Using compare power against vehicle weight helps you judge how quick the car should feel, since power-to-weight is often a better acceleration indicator than torque alone.