A carpenter's square is a type of square, also called a framing square, that is L-shaped and used mainly for squaring up sections of work such as wall studs and sole plates – in other words, ensuring that they are at right angles to each other.

The carpenter's square has a 24-inch blade and a 16-inch tongue, forming a right (90-degree) angle. The blade and tongue are marked with inches and fractions of an inch, or their metric equivalents. The blade and the tongue can also be used as a rule or a straightedge. Tables and formulas are printed on the blade for making quick calculations such as determining area and volume.