One inch equals 2.54 cm.

2.54 times 2.54 times 2.54 equals 16.387064

Therefore 16.387064 cc equals 1 cubic inch

So for a 1.8 cubic inch engine it is 29.49 cc .... 16.387964 times 1.8

So for a 50 cc engine equals 3.05118 cubic inches .... 50 divided by 16.387064

Enjoy

Jim