Stair Calculator

Number of Steps
14
–

📐 Details

Actual Riser Height–
Total Run (horizontal length)–
Stringer (diagonal) Length–
Stair Angle–

What Is a Stair Calculator?

This calculator determines the number of steps, exact riser height, total horizontal run, and stringer length needed for a staircase, based on total rise (floor-to-floor height) and your target riser and tread dimensions.

How to Use the Stair Calculator

  1. Enter the total rise (vertical floor-to-floor height).
  2. Enter your target riser height (typically 7-7.75 inches for comfort and code compliance).
  3. Enter your tread depth (typically 10-11 inches).

Stair Calculation Formulas

Number of Steps
Steps = Round(Total Rise ÷ Target Riser Height)
Actual Riser Height
Actual Riser = Total Rise ÷ Number of Steps
Stringer Length
Stringer = √(Total Rise² + Total Run²)

Worked Example

Example: 108 in Total Rise, 7.5 in Target Riser, 10 in Tread

Number of steps: 108 ÷ 7.5 ≈ 14.4 → rounds to 14

Actual riser height: 108 ÷ 14 ≈ 7.71 in (evenly distributed)

Total run: 13 treads × 10 in = 130 in (one fewer tread than risers)

Stringer length: √(108² + 130²) ≈ 169 in

Understanding Your Results

All risers in a staircase must be equal height for safety — this calculator rounds to a whole number of steps and recalculates the exact riser height so it divides evenly into the total rise. Building codes typically specify maximum riser height and minimum tread depth; always verify against your local building code.

Common Mistakes to Avoid

  • Building stairs with uneven riser heights, which is both a code violation and a serious trip hazard.
  • Not checking local building code requirements for riser height and tread depth limits before construction.

Frequently Asked Questions

Divide the total rise (floor-to-floor height) by your target riser height, then round to the nearest whole number, since you can't have a fractional step.

Many building codes specify a maximum around 7.75 inches, with 7-7.5 inches often considered comfortable — always check your specific local building code requirements.

The stringer is the diagonal structural board supporting the stairs — knowing its length helps with material purchasing and cutting.

Uneven riser heights are a serious trip hazard and violate building codes in most jurisdictions — consistency is critical for stair safety.

Common tread depths range from 10-11 inches, providing adequate foot space — check your local building code for specific minimum requirements.