Concrete Step Calculators

Concrete for steps does not scale with the number of steps. It scales with the square of it.

The bottom step carries the full depth of every step above it. Four steps is ten step-blocks of material, not four. Multiply one step's volume by the step count — which is what most step calculators do — and you will be short by more than half on anything above three steps.

The correct figure is rise × run × n(n+1)/2, times the width.

Two checks, and they are different

Code. The IRC allows a maximum 7¾″ rise and requires at least a 10″ run. There is a third rule that catches more people than either: no more than ⅜″ variation between the tallest and shortest riser in one flight. With concrete you get exactly one attempt at that.

Comfort. Carpenters check 2 × rise + run and want the result between 24 and 25 inches. Steps that satisfy code can still feel wrong underfoot — too quick, or a stretch that people take two at a time — and this is the check that catches it.

Get the total rise first, then divide

Measure from the finished landing down to the finished grade, then divide by a whole number of steps. Fudging the bottom riser to absorb a leftover inch is precisely what the ⅜″ rule exists to prevent, and it is exactly what people do when they work the other way round.

They project further than you think

Four steps at an 11″ run stick out 3 ft 8 in from the wall. That measurement is the one that collides with paths, driveways and property lines, and it is usually discovered after the forms are built.

Under them

Compacted gravel across the whole footprint, below the frost line at the front edge. Steps that heave separate from the house at the top and open a gap that grows a little every winter.