3-4-5 Square, Diagonals, Slope and Stepped Footings

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Opens on the book's own wall. Change any number to your own and press Calculate.

Leg A m or ft

Leg B m or ft

Diagonal you measured optional

Rectangle length e.g. the footing outline

Rectangle width

Fall along the line mm (or inches)

Length of the line m (or ft)

Fall measured in

Ground drops along the wall mm

Step height (one course) mm

Footing thickness mm

Enter the legs of your corner and press Calculate.

From the book, Chapter 2. Diagonal = √(A² + B²). 3-4-5, 6-8-10 and 0.9-1.2-1.5 all make a right angle. A rectangle is square when its two diagonals match.

Steps follow the UK guidance for strip footings: a step no taller than the footing is thick, and an overlap of the larger of twice the step, the footing thickness, or 300 mm. Prices are illustrative US home-center prices from October 2026, shown without a currency sign; put in your own. Everything stays in your browser: no sign-up, nothing stored.