Wheel offset Math, who wants to check my numbers

First post and just trying to dial in my set of wheels to put on and I did the calculation myself but want to see if some one can confirm my numbers.

Current rear
20x10 et 42
2.5" lip
.5" center
7" inner barrel

Front 
20x8.5 et 40
1" lip
.5" center
7" inner barrel
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New setup rear
20x10.5 et 33
3" lip
.5" center
7" inner barrel

Front
20x10 et 21
2.5" lip
.5" center
7" inner barrel
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give or take, depending how you round off:

20x10 22
20x10.5 27

20x10.5 +36
- subtract ~6mm for adding .5 inch of lip
20x10 +21
- subtract ~19mm for adding 1.5 inches of lips

Thanks for the help, now to get some lips ordered.


Sent from my iPad using VIPStyleCars

[QUOTE=Prime;503542]20x10.5 +36
- subtract ~6mm for adding .5 inch of lip
20x10 +21
- subtract ~19mm for adding 1.5 inches of lips[/QUOTE]
correct. think I was drunk.