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How to Calculate the CCs on a Motorcycle Engine

by Chris Gilliland

For more than a century, the cubic centimeter has been the unit of choice for measuring a motorcycle's engine displacement--the amount of air that is moved by the engine's pistons within a single revolution. This measurement is determined by the size of the engine's cylinders and the distance the pistons move within them, measurements referred to as the bore and stroke of the engine. These measurements are used in simple formula to determine the engine's displacement.

Step 1

Locate the bore and stroke specifications of your motorcycle's engine. These are often listed in your motorcycle's owner's manual under "Technical Specifications." A 1976 Kawasaki KZ750, for example, has a bore and stroke measurement of 78.0 mm x 78.0 mm--the cylinder bore (or diameter) is 78mm and the piston stroke, from top of piston to bottom of cylinder head when the piston is at the lowest part of its stroke, is 78mm.

Step 2

Multiply the bore against itself, multiplied by the stroke, multiplied by 3.141593. For example: 78 mm (bore) X 78 mm (bore) X 78 mm (stroke) X 3.141593 = 1490849.241336.

Step 3

Divide the result by the number of cylinders in the engine. For example, a 1976 KZ750 has a two-cylinder engine. 1490849.241336 ÷ 2 = 745424.620668.

Divide the result by 1000 and round up to the nearest number to calculate the engine's total displacement. For example: 745424.620668 ÷ 1000 = 745.424.620668 or 745 cc.

Tip

• Harley-Davidsons are commonly measured in cubic inches--an 81-cubic-inch Harley V-Twin engine is 1327 cubic centimeters. Multiply cubic inches by 16.387 to determine cubic centimeters. Multiply cubic centimeters by .061 to determine cubic inches.

Items you will need

• Owner's manual