best way is to look at manufactureres specs, if they are not there, you can calculate the total cubic mass of the subs. Now this number would be much higher than the real displacement, but it would give you the idea.
Just find the formula to find the volume of a culinder and do the rest of the math. It is a complex equation tho.
Just find the formula to find the volume of a culinder and do the rest of the math. It is a complex equation tho.