Estimate engine torque from displacement and BMEP, or reverse-solve BMEP or cc, with two- and four-stroke physics, unit conversions, specific torque, and power.
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cc To Torque Formula
The calculator uses brake mean effective pressure (BMEP): T = BMEP ร Vd / (2ฯn), with Vd in mยณ, BMEP in pascals, and n = 2 for a four-stroke or 1 for a two-stroke engine. Rearrange the same relationship to solve BMEP or displacement. Displacement alone cannot determine torque.
Variables:
- T is the torque (Nm)
- ES is the engine displacement (cc)
- k is an assumed constant (Nm/cc) chosen for the engine and operating point (not a universal conversion)
The table below illustrates the equivalent linear form T โ ES ร k for one stated operating-point assumption. For a four-stroke engine, k = 0.10 Nm/cc corresponds to BMEP โ 12.5664 bar; it is not a universal conversion. In the calculator, enter BMEP at the intended operating point. Engine speed is optional and supplies the power estimate P = T ร 2ฯ ร rpm / 60.
| Displacement (cc) | Torque (Nm) | Torque (ft-lb) |
|---|---|---|
| 49 | 4.9 | 3.615 |
| 50 | 5.0 | 3.688 |
| 100 | 10.0 | 7.376 |
| 125 | 12.5 | 9.220 |
| 150 | 15.0 | 11.063 |
| 200 | 20.0 | 14.751 |
| 250 | 25.0 | 18.439 |
| 300 | 30.0 | 22.127 |
| 350 | 35.0 | 25.815 |
| 400 | 40.0 | 29.502 |
| 450 | 45.0 | 33.190 |
| 500 | 50.0 | 36.878 |
| 600 | 60.0 | 44.254 |
| 650 | 65.0 | 47.942 |
| 700 | 70.0 | 51.629 |
| 750 | 75.0 | 55.317 |
| 800 | 80.0 | 59.005 |
| 900 | 90.0 | 66.381 |
| 1000 | 100.0 | 73.756 |
| 1200 | 120.0 | 88.507 |
| Example only (assumes a linear relation T = k ร cc with k = 0.10 Nm per cc). Actual torque depends on engine design and RPM. Unit note: 1 Nm = 0.737562 ft-lb. | ||
What is Torque?
Torque is a measure of the rotational force that an engine can produce. It is a crucial factor in determining an engine's ability to do work, such as moving a vehicle. Torque is typically measured in newton-meters (Nm) or foot-pounds (ft-lb) and is a function of engine size, design, and other factors.
How to Calculate Torque from cc?
Select torque, BMEP, or displacement as the solve target. For torque from displacement, follow these steps.
- First, determine the engine displacement (ES) in cubic centimeters (cc).
- Choose the two- or four-stroke cycle and enter the BMEP for the engine operating point. Select the units attached to each quantity; changing an input unit converts its current value.
- Use T = BMEP ร Vd / (2ฯn), converting cc to mยณ by multiplying by 0.000001 and bar to pascals by multiplying by 100,000.
- Finally, calculate the estimated torque (T) in newton-meters.
- After inserting the variables and calculating the result, you can check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Engine displacement (ES) = 1000 cc
For a four-stroke engine, using BMEP = 12.5663706 bar (equivalent to k โ 0.10 Nm/cc), the brake torque is:
T โ 1,256,637.06 Pa ร 0.001 mยณ / (4ฯ) โ 100 Nm. Select Calculate to obtain the result; editing inputs retains the previous result until recalculated.
