Deck Stair Calculator
Calculate the number of steps and stair stringers.
How It Works
Risers = ceil((Height × 12) ÷ Riser height). Treads = Risers − 1. Stringers = ceil((Width × 12) ÷ 24) + 1.
Example
A 3 ft deck with 7 in risers: 6 risers, 5 treads, and 3 stringers for a 3 ft wide stair.
Frequently Asked Questions
What riser height is legal?
Most codes cap risers at 7.75 in and treads between 10–11 in deep.
Why is there one less tread?
The top landing serves as the first tread, so you need risers − 1 actual treads.
How are stringers spaced?
Stringers are typically spaced no more than 24 in on center — 3 for a 36 in stair.