Squaring Calculator
Find the diagonal that makes a rectangle square, to check foundations, decks and framing, to the nearest 1/16 in.
Change the values and press Calculate to work out your own figures.
Enter the length and width.
Show the working
- diagonal = √(length² + width²)
How to use it
Enter the length and width.
Lengths can be decimals, fractions or tape entries such as 12' 6 1/2" (in feet or inches). Prices are optional.
Key facts
diagonal = √(length² + width²); both diagonals equal when square
3-4-5
Mark 3 ft along one side and 4 ft along the other; the corner is square when the points are 5 ft apart (or 6-8-10, 9-12-15).
Questions
What's the diagonal of a 30 × 40 ft rectangle?
50 ft.
Formulas
diagonal = √(length² + width²); both diagonals equal when square
Sources
Limitations
- Material densities are typical values (the midpoint of the commonly published range); real loads vary with moisture, grading and compaction, so check with your supplier or type in their density.
- Tank results are the geometric volume; real tanks have wall thickness and fittings.