Obviously it depends on the type of greenhouse, but in the one I have the glass in the side is (starting at the floor), large, small, small. In the roof again (starting at the eaves) it is large small,small. You would need to see how many of each size you have available. For the above system you would need 4 times the number of spaces in the sides of small panes and twice the number of large times the number of spaces.
So in a greenhouse with 4 spaces for glass in the sides, you would need 4 x 4 = 16 small and 4 x2 =8 large. Then there is the gable end and the door end.
I suggest you count the number of pieces of glass in each size and see if you can work out the arithmetic as above.
Our 3 glasshouses are all different arrangements!