Stair Stringer Calculator

Stair Stringer Calculator

Getting stair riser heights uniform and code-compliant is one of the most important safety details in any staircase build - this calculator works out an exact, evenly-divided riser layout from your total vertical rise.

Formula

Number of Risers = round(Total Rise / Target Riser Height)
Actual Riser Height = Total Rise / Number of Risers
Number of Treads = Number of Risers - 1

Example

A 108-inch total rise, targeting a 7.5-inch riser height:

Risers = round(108/7.5) = 14 → Actual Riser Height = 108/14 = 7.714", with 13 treads

Why Uniformity Is a Serious Safety Requirement

Most residential building codes require riser heights within a specific range (commonly capping around 7.75 inches) and mandate that all risers within a single staircase be nearly identical - typically within 3/8 inch of each other. Even small inconsistencies between individual risers create a genuine trip hazard, since people unconsciously expect uniform step height once they've taken the first few steps of a staircase.

Always Check Local Code

This calculator gives a mathematically even riser distribution, but exact code requirements for riser height, tread depth, and headroom clearance vary by jurisdiction - always verify against your specific local building code before finalizing stair construction dimensions.