Stair Calculator
Calculate stringer length and materials for deck or interior stairs.
Stair Calculator
What This Calculator Does
The Stair Calculator (material version) computes the lumber and materials needed to build a set of stairs, including tread surface area, stringer linear footage, and total step count. Enter the number of steps, stair width, and tread depth to get a complete material takeoff for stair construction.
Building code-compliant stairs require careful material planning. Each tread must support a minimum of 300 lbs concentrated load. Stringers (the angled supports) are typically cut from 2x12 pressure-treated lumber and must be spaced no more than 36 inches apart for residential stairs.
This calculator focuses on the material quantities for stair construction: tread surface area (for finish flooring), stringer linear footage (for purchasing stringer lumber), and rise information.
How to Use
- Determine the number of steps using the Stair Rise and Run Calculator first.
- Measure the stair width (minimum 36 in for main stairs, 24 in for secondary).
- Select the tread depth (standard 10-11 inches per IRC code).
- Enter all values into the calculator fields above.
- Click "Calculate" to get the tread area for flooring and stringer LF for lumber ordering.
Reference Table
| Steps | Width | Tread Area | Stringer LF | Material Cost |
|---|---|---|---|---|
| 10 steps | 36 in | 30 sq ft | 22 LF | $100-$250 |
| 13 steps | 36 in | 39 sq ft | 28 LF | $130-$325 |
| 13 steps | 48 in | 52 sq ft | 42 LF | $175-$430 |
| 16 steps | 36 in | 48 sq ft | 35 LF | $160-$400 |
| 16 steps | 48 in | 64 sq ft | 52 LF | $215-$530 |
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