An exact angle measurement is not possible due to the large gap between the two halves and the flexibility of the plastic. (see photos). The gap can be closed with a little effort and the plastic spring opens again when you let go. This means that if you run a saw or even a pencil along the edge, the angle will actually change. Other reviewers have also mentioned the gap. I didn't even dare to take it out of the packaging. Admittedly, I wasn't expecting to get a $20 plastic precision tool, but the one I got isn't even useable for its intended purpose, unless you're building a doghouse, maybe. . ;-P