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Concrete Stairs Calculator

Use this concrete stairs calculator to find the volume of concrete you'll need for a concrete stairs project.

Clear
Concrete needed1.3071 cubic yards35.292 cu ft, including 10% waste
Bags of 80 lb mix59
Total rise35 in2 ft 11 in
Total run55 in4 ft 7 in
Stair angle32.471°comfortable stairs land between 30° and 37°
2 × rise + run25 ininside the classic 24–25 in comfort rule
Rise checkwithin codemost US codes cap a riser at 7¾ in
Run checkwithin codemost US codes want at least 10 in of tread
Steps5

The method

volume = width × run × rise × n(n + 1) ÷ 2

Why the triangular number

Think of a solid staircase as vertical slabs standing side by side: the first is one rise tall, the second two, and so on to n. Their total height is 1 + 2 + … + n = n(n + 1) ÷ 2 rises, so the volume is width × run × rise × that. Five 7-inch steps come to fifteen rises, not five.

The rise and run also have to be comfortable and legal. Most US codes cap the riser at 7¾ inches and want at least 10 inches of tread; the old carpenter’s rule that twice the rise plus the run should land between 24 and 25 inches gets you a stair that feels right.

Every step in a flight must match. A single riser even a ⅜ inch different from its neighbours is a trip hazard and will fail inspection.