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Stair Calculator

Number of steps, riser height, tread run and stringer length from the total rise.

How it's calculated

Risers = total rise ÷ maximum riser height, rounded up; each riser is then total rise ÷ risers. There is one fewer tread than risers. Total run = treads × tread depth. Stringer length = √(rise² + run²). The defaults are the International Residential Code limits (7¾-inch maximum riser, 10-inch minimum tread). Local codes can differ, so check yours.

Example

A 108-inch rise: 108 ÷ 7.75 = 13.9, so 14 risers of 7.71 inches and 13 treads; at 10 inches each that is a 130-inch run.

Residential code limits (IRC R311.7)

ItemLimit
Riser heightmax 7¾"
Tread depthmin 10"
Headroommin 6 ft 8 in
Stair widthmin 36"
Riser variation in a flightmax ⅜"

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