When measuring oil, acrylic or any art on a stretcher bars for framing
I recommend that you measure top, middle and bottom & left middle and right like shown below.
Canvas on stretcher bars tend to bow inward in the middle because of the pressure from stretching the canvas especially if there is no center brace.
This is why we recommend measuring like this.
With these 6 measurements it will help make the frame properly.
The Gallery at Brookwood
5755 Cousins St
Austell, GA 30168