Calculate arbitrary rotate with Measure tool in Photoshop

It’s always nice to get the horizon in a picture to run dead straight. Sometimes the photographer hasn’t always had his camera that way. Similarly maybe you want a straight line in a building to be exactly horizontal or vertical. The image needs to be rotated arbitrarily … but by how much? Get the Measure tool in Photoshop (I) and drag it exactly along the line that needs to be aligned. Now go Image > Rotate Canvas > Arbitrary and there you will see the exact measurement. Hit Return to rotate!