Stair Stringer Calculator

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Calculate the dimensions and layout for cutting stair stringers. Enter the total rise, tread depth, and number of risers to determine the stringer board length, throat depth, and each notch cut dimension. Proper stringer cuts are essential for safe, even stairs.

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Enter Your Measurements

Results

Stringer Length

176.8

inches

Board Length Needed

15

feet

Riser Height (each)

7.71

inches

Number of Treads

13

treads

Total Run

130.0

inches

Maximum Notch Depth

7.75

inches

Unit Hypotenuse

12.63

inches

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Formula

Riser Height = Total Rise ÷ Risers | Stringer = √(Rise² + Run²) × Risers | Min Throat = Board Width - Notch Depth ≥ 3.5 in

How to Use This Calculator

How to Use

  1. 1

    Enter the total rise (floor to floor height in inches).

  2. 2

    Enter the tread depth (run per step).

  3. 3

    Enter the number of risers (from the stair calculator).

  4. 4

    Enter the stringer board width (2x12 is 11.25 inches actual).

Frequently Asked Questions

Frequently Asked Questions

What size board for stair stringers?

Most stair stringers are cut from 2x12 lumber (actual 1.5 in × 11.25 in). This provides adequate throat depth (the remaining wood after notches) of at least 3.5 inches per code.

How many stringers do I need?

Use 3 stringers for stair widths up to 36 inches: one on each side and one in the center. For wider stairs, add a stringer every 16 to 18 inches.
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About This Calculator

This calculator uses the formula: Riser Height = Total Rise ÷ Risers | Stringer = √(Rise² + Run²) × Risers | Min Throat = Board Width - Notch Depth ≥ 3.5 in. All calculations follow industry-standard methods. Results are estimates — always verify with a licensed professional for structural or code-compliant work.

Built and maintained by the CalcSmart team. Last updated March 2026.

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