if an engine has a displacement of 1.8 liters, that is for all the cylinders combined. if you do the math using bore and stroke you'll see the whole number of displacement can be divided by the number of cylinders. So in a 1.8L 4 cylinder engine, the displacement for each cylinder would roughly be a quarter of the total engine displacement. in a 6cyl, 1/6 of the total displacement equals individual cylinder displacement. same with a 8cyl and so on.
I've already divided that into 4...
DISP = 1780 / 4 = 445 cm^3 = 0.000445 m^3