Compression ratio can it be measured without removing cylinder head?

Simple answer, no not really.

It has to come off to make volumetric measurements of bore and also the head otherwise it is a wet finger in the air / guess.

Yes.

To determine your actual cylinder capacity (the larger figure in the equation), the piston needs to be at BDC.  At that point your exhaust valve has started to open. You therefore cannot fill to the plug hole as the fluid will seep out.

Disconnect the EX valve from the train as simply as you can; tappet, rocker, chain, gear…. Then rotate to measured BDC to give full stroke position. 

What is the reason for making this static measurement ? Curiosity or suspicion?? Jon

Even if you don't know the cubic capacity.

Fill the cylinder with some light oil when the piston is at bottom dead centre and measure the quantity.  Then fill the cylinder at top dead centre and measure the quantity.  Divide the first measurement by the second and this will give the compression ratio.

As long as you know the capacity of the cylinder all you need to do is measure the combustion chamber capacity - I use water, that way you can blow it out with compressed air and don’t have to remove the head.

john

.....must be made with head on. I use a graduated burette filled with thinned ATF. Level plug hole to assure filling chamber. Piston at TDC.  Fill to bottom of plug hole. Grease around top of piston so it doesn't leak past.