How to Calculate the Cubic Inches of a 4 stroke engine
Take the size of your engine in liters and multiply that number by 61.0237 to get the size of your engine in cubic inches.
Take your engine size in cc's and multiply that number by 0.0610237. This will give you the size of your engine in cubic inches. You can also use the formula in Step 1 and divide by 1,000.
Take your bore squared (multiplied by itself) times your stroke times 0.7854 times the number of cylinders in your engine to arrive at your cubic inches (cid). Here is that formula simplified: (bore) x (bore) x (stroke) x 0.7854 x (# of cylinders) = cubic inch displacement