728 × 90 Leaderboard

320 × 100 Mobile Banner

Stair Calculator

Calculate risers, treads, and total run for building stairs.

Last updated: June 13, 2026

Calculator

Total Rise (floor to floor)

inches

Desired Riser Height

inches

Results

Number of Risers14

Actual Riser Height7.71"

Code: 4"-7.75" per riser

Tread Depth17.29"

Using 7/11 rule (riser + tread ≈ 25")

Total Run224.7" (18.7 ft)

Stair Angle24.1°

Comfortable: 30-37°

How to Use This Calculator

1Enter the total rise (floor to floor) in inches.
2Enter your desired tread depth in inches.
3View number of risers, riser height, stringer length, and code check.

Formula Explanation

Stair calculations ensure uniform riser height and proper tread depth within building code limits.

Number of Risers = Total Rise ÷ Ideal Riser Height Actual Riser = Total Rise ÷ Number of Risers Stringer Length = √(Total Rise² + Total Run²)

Variables:

Total RiseVertical distance from floor to floor in inches

Tread DepthHorizontal depth of each step (typical: 10-11 inches)

Riser HeightVertical height of each step (code: max 7.75 inches)

Worked Examples

108-inch total rise, 10.5" treads

1. Risers = 108 ÷ 7.5 = 14.4 → 15 risers
2. Actual riser = 108 ÷ 15 = 7.2 inches
3. Run = 14 treads × 10.5" = 147"
4. Stringer = √(108² + 147²) = 182.4"

Result: 15 risers at 7.2", stringer 15.2 ft — code compliant

Why Use This Calculator

Ensures building code compliance for safe stairs.
Calculates exact stringer length for lumber ordering.
Uniform risers prevent tripping hazards.
Works for interior and exterior stairs.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

Tips & Best Practices

Building codes typically require 7¾" max riser height and 10" min tread depth.
Every riser must be the same height — uneven risers cause falls.
Add a nosing overhang of ¾" to 1¼" for comfort.
Minimum stair width is usually 36 inches per code.

Common Mistakes to Avoid

❌ Rounding riser count and getting uneven final step.

✅ Always round the number of risers, then recalculate the exact riser height. Every riser must be identical.

❌ Forgetting to account for the finish floor thickness.

✅ Measure total rise from finished floor to finished floor. Subtract or add for flooring not yet installed.

Frequently Asked Questions

What is the ideal riser height for stairs?

The ideal riser height is 7-7.5 inches. Building codes typically allow a maximum of 7¾ inches. The 7-11 rule (7" riser, 11" tread) is the most comfortable combination.

How do I calculate the number of stairs I need?

Divide the total rise (floor to floor height in inches) by your ideal riser height (7-7.5 inches). Round to the nearest whole number, then divide the total rise by that number for the exact riser height.

What is a stair stringer?

A stringer is the diagonal structural board that supports the treads and risers. You need at least two, spaced no more than 36 inches apart. A third stringer is added for stairs wider than 36 inches.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

Embed This Calculator

Add the Stair Calculator to your website for free. Copy the code below and paste it into your HTML.

Width

Height

<iframe src="https://redicalc.com/embed/construction/stair-calculator" width="100%" height="600" style="border:none;border-radius:12px;box-shadow:0 1px 3px rgba(0,0,0,0.1);" title="Stair Calculator — RediCalc.com" loading="lazy" allowtransparency="true"></iframe>

Preview embedFree to use · Attribution link included

Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.

160 × 600Skyscraper