will a bmw 5 series door glass fit a 7 series door, as they look the same?

The 7 is a little longer in the back than the 5.

For example

1992 5 series:

DOOR WINDOW, REAR LEFT 51 34 1 944 087

1992 7 series

DOOR WINDOW, REAR LEFT51 34 1 928 361

Not the same.

Hard to tell since you don't mention what year of 5 series or 7 series you are talking about. But usually there are not many exterior pieces that swap between different models of BMW.

But here are 3 options:

1. You could go to www.realoem.com, which is an online bmw parts catalog and compare the part numbers for the windows in question.

2. If you want to do a quick check, just outline one of the windows of one car on some cardboard and then compare it to the other car.

3. Ask the parts department at your local BMW dealer and they will likely be able to tell you if you give them the year and model numbers of the cars.

It will work if it is NOT an il series