Input your engine bore (piston/cylinder size) and stroke (crank) in the boxes below. If you want to check the dispacement for another engine, change the number of cylinders accordingly. Click the displacement button to see your calculated engine dispacement. There's also a metric converter down below Engine Item MM Inches Measurement Bore Stroke # of cylinders 1 2 3 4 5 6 8 10 12 Your Displacement is : Click For Displacement       mm to inch conversion mm inch fraction Enter a value in either the mm or inches box, then click the mouse anywhere outside of that box, and it will instantly calculate the other values for you.

script taken from http://www.johnmaherracing.co.uk/enginecalc.htm