Steel square-up / diagonal calculator
Enter width and height to get the required diagonal for a square rectangle, then enter a measured diagonal to see how far a panel or frame is out of square.
Enter width and height to check square.
Formula & assumptions
Required diagonal = √(width² + height²). A rectangle is square when both corner-to-corner diagonals are equal to this value. Enter a measured diagonal to see the out-of-square difference (measured − required); a positive number means the measured diagonal is long.
Layout aid only. Always check both diagonals in the field and compare to your tolerance in the contract documents/spec before proceeding.
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