Stair Tread Calculator
Calculate tread depth, nosing overhang, and total tread material needed. Supports different tread materials and widths.
How It Works
Enter your number of steps, stair width, and tread material type. The calculator determines the tread depth (run + nosing overhang), nosing projection, total number of tread boards needed, and board feet of material required. It accounts for different material thicknesses and standard lumber dimensions. The result includes a shopping list with common retail sizes.
Frequently Asked Questions
What is the minimum tread depth?
IRC 2018 requires a minimum tread depth of 10 inches measured from nosing to nosing (or nosing to riser face if no nosing). The actual tread board may be 11-11.5" to include the nosing overhang.
How much nosing overhang should treads have?
Standard nosing overhang is 3/4" to 1-1/4". IRC code requires between 3/4" and 1-1/4" of nosing projection if risers are used. Nosing must be uniform throughout the staircase (max 3/8" variation).
What thickness should stair treads be?
For residential stairs with stringers 16" apart or less, 5/4 (1") thick treads work. For wider stringer spacing or heavy-duty applications, use 2" (1.5" actual) thick treads. Hardwood treads are typically 1" thick.
Can I use composite decking for stair treads?
Yes, composite decking works well for outdoor stair treads. Use stair-specific composite tread boards (usually 1" thick with a bullnose edge) rather than standard deck boards, which may not meet code for thickness.