The biggest mistake made with a tape measure is neglecting the housing. The housing is the plastic or metal case it comes in — and not enough people pay attention to it.
Many people lay out the tape, and when it gets to a corner, they curl or bend the tape. While holding the housing in their hand, they try to eyeball the number in the fold.
The housing is actually meant to be incorporated into a given measure. Typically, the housing of a standard tape measure is about 3 inches, but the exact measure is on the back.
With a wall-to-wall or corner measurement, simply use your housing to fill up the end space. Note the measurement on the tape, then add the housing number to it, ensuring accuracy.