3-4-5 Squaring Calculator
Verifies 90-degree angles from two measured wall lengths using the Pythagorean theorem
Length of the first wall
Length of the second wall
Acceptable margin of error for squareness check
The diagonal measurement needed for a perfect 90-degree angle
The nearest 3-4-5 triangle ratio for your measurements
Whether the corner forms a 90-degree angle within your tolerance
Frequently Asked Questions
What is the 3-4-5 rule for squaring corners?
The 3-4-5 rule is a practical application of the Pythagorean theorem. If you measure 3 feet along one wall and 4 feet along the adjacent wall, the diagonal between those two points should be exactly 5 feet if the corner is a perfect 90-degree angle. Any multiple works too (6-8-10, 9-12-15, etc.).
How accurate is the 3-4-5 method?
The 3-4-5 method is mathematically exact. Accuracy depends on your measurement precision. Using larger multiples (like 9-12-15 or 12-16-20) increases accuracy because measurement errors become a smaller percentage of the total. For framing, a tolerance of 1/8 inch is standard.
When should I use the 3-4-5 squaring method?
Use it whenever you need to verify or create a 90-degree angle: laying out foundations, framing walls, installing decks, setting fence posts, tiling floors, or any construction where square corners matter. It requires only a tape measure and no special tools.
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