Enter the bore size (in) and the stroke length (in) into the Calculator. The calculator will evaluate the Bore To Stroke Ratio. 

Bore To Stroke Ratio Formula

BTS = B / S


  • BTS is the Bore To Stroke Ratio (in/in)
  • B is the bore size (in)
  • S is the stroke length (in)

To calculate Bore To Stroke Ratio, divide the bore size by the stroke length.

How to Calculate Bore To Stroke Ratio?

The following steps outline how to calculate the Bore To Stroke Ratio.

  1. First, determine the bore size (in). 
  2. Next, determine the stroke length (in). 
  3. Next, gather the formula from above = BTS = B / S.
  4. Finally, calculate the Bore To Stroke Ratio.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

bore size (in) = 20

stroke length (in) = 10


What is the significance of the Bore to Stroke Ratio in engines?

The Bore to Stroke Ratio is crucial in determining an engine’s efficiency, power, and overall performance. A higher ratio often indicates a more powerful engine that can achieve higher revolutions per minute (RPM), while a lower ratio may suggest an engine designed for higher torque.

How does the Bore to Stroke Ratio affect fuel efficiency?

Engines with a higher Bore to Stroke Ratio tend to have shorter strokes, which can lead to better fuel efficiency due to less frictional losses during piston movements. However, the actual fuel efficiency also depends on other factors such as engine design and operating conditions.

Can the Bore to Stroke Ratio impact the lifespan of an engine?

Yes, engines with a lower Bore to Stroke Ratio, which typically have longer strokes, may experience less stress on the pistons and connecting rods, potentially leading to a longer engine lifespan. However, maintenance, usage, and build quality also play significant roles in determining an engine’s lifespan.

Is it possible to modify an engine’s Bore to Stroke Ratio?

Modifying an engine’s Bore to Stroke Ratio is possible through engine tuning or rebuilding, which may involve changing the pistons, crankshaft, or cylinder bore. However, such modifications require careful consideration and expertise to ensure engine balance and prevent potential damage.