I'm assuming compression ratio is the ratio of the combustion chamber volume with the piston at bottom dead center to the combustion chamber volume with the piston at top dead center.
Anyways, what measurements are required to calculate compression ratio? Seems to me in addition to the bore and stroke you'd need the head gasket thickness need to know the volume between the top of the piston (@TDC) and dome of the head, which can change depending on the design of the top of the piston and headwork. Or is it just measured by air pressure difference at BDC and TDC? Eh but you'd need perfect compression for accurate results.
Say you've got 11:1 pistons and get some headwork, how do you calculate your new compression ratio?
Bottom line: how is compression ratio measured?

 

Couldnt you just get a compression testor and see what its running at?
Sure it calculates it in different terms, but it still tells you how close to stock you are..
I just did mine and a stock Prelude Si runs at (9.8:1) or 160# on the compression testor.
when I did my test I ran : 160,150,150,160 (cylinders 1-4) pretty good for 137k miles
*shrug