I'd go with wabi on this one.

Well again, this was made on Print Shop, not actually shot on a range with a rifle. When I set the scale on it, the group was suppose to be 1 1/8th of an inch. So most of you are real close and must measure a target basically the same way I do.

I heard FG measured it and it was about 1/4". Just teasing because I know he can take it.

I came up with 1.125" when I looked at it (and before I read Dave's answer). Center to center is the way I learned to do it.

I've always measured center to center on the farthest two holes. However,most of the time my measurements are more like: "yep, that'll kill a deer."

1 1/8"

I measure from outside to outside minus the caliber,but how do you measure one like this??

Outside of the 2 farthest edges minus bullet diameter is the same as center to center so either way is good.
However i believe Wabi is correct on this one

Yea Herman, with one like that you measure the largest diameter of the hole and subtract the caliber...Heck with Cay's example, I just grabbed a ruler and put it up to the screen....He threw me a curve, noticed today that an inch isn't a inch...