Deck Stair Calculator

How the Deck Stair calculator works

Formula. Number of stairs = total rise / desired rise, rounded up. Actual rise = total rise / number of stairs. Run per step = actual rise × 1.5. Total run = run × (number of stairs − 1).

Example. A 36 inch rise with a 7 inch target is ceil(36 / 7) = 6 stairs. Actual rise is 36 / 6 = 6 inches. Run per step is 6 × 1.5 = 9 inches. Total run is 9 × 5 = 45 inches.

Limitation. The 1.5 run multiplier is a fixed rule in the script and is not a building-code check for riser and tread limits.