What is the ideal riser height?

Residential building codes in the US typically require risers between 4 and 7.75 inches (10–19.7 cm). A comfortable standard is 7 inches. The sum of rise + run should be between 17 and 18 inches for comfortable climbing.

What is the minimum tread depth?

Most codes require a minimum tread depth (run) of 10 inches (25.4 cm), measured from nosing to nosing. A depth of 11–12 inches is considered comfortable.

How is stringer length calculated?

Stringer length = √((total rise)² + (total run)²). This is the diagonal hypotenuse of the staircase triangle, representing the minimum board length needed for the stringer.

Why does the calculator adjust my riser height?

The number of steps must be a whole number. The calculator divides total rise by your desired riser to find the nearest whole-number step count, then recalculates the exact rise per step so all risers are equal.

What is the 7-11 rule for stairs?

The 7-11 rule states that rise + run should equal approximately 17–18 inches (some say exactly 18). A 7-inch rise and 11-inch run is a classic comfortable stair proportion.

Does this tool account for headroom or landing size?

No — this calculator focuses on step geometry (rise, run, count, stringer). Headroom clearance and landing dimensions depend on your specific framing and are best verified with your local building code.

How do I calculate stair stringers from rise and run?

Divide the total rise by your target riser height (typically 7 inches) and round to a whole number — that is the step count. Individual rise = total rise ÷ step count. Total run = (step count - 1) × tread depth. Stringer length = √(total rise² + total run²) using the Pythagorean theorem. Use a framing square to mark the rise-and-run notches on a 2×12 stringer board.

Stair Calculator

Calculate stair rise, run, number of steps, and stringer length from total rise and desired step dimensions.

Stair Dimensions

Total Rise (inches)

Vertical height from bottom floor to top landing.

Desired Riser Height (inches)

Typical range: 6–8 in (15–20 cm).

Tread Depth (Run) (inches)

Typical minimum: 10 in (25.4 cm). 11–12 in is comfortable.

Results

Enter dimensions and press Calculate

Stair Diagram

Diagram updates after you calculate.

Summary

A free online stair calculator that determines the optimal number of steps, individual rise and run dimensions, and diagonal stringer length for any staircase. Enter your total rise height and preferred tread depth to get code-compliant step dimensions. Supports both imperial (inches/feet) and metric (cm/mm) units.

How it works

Enter the total rise — the vertical height from floor to floor (or top of landing).
Enter your desired riser height (typically 6–8 inches or 15–20 cm).
Enter your desired tread depth (run), typically 10–12 inches or 25–30 cm.
The calculator finds the ideal number of steps and adjusts the actual rise to fit evenly.
Results include individual rise, run, stringer length, total run, and a step-by-step summary.

Use cases

Planning deck stairs for a backyard project.
Designing interior staircases to meet building code requirements.
Estimating stringer lumber length before purchasing materials.
Verifying rise-to-run ratios comply with residential code (7-11 rule).
Calculating outdoor concrete steps from a porch to grade.
Double-checking stair geometry before pouring footings.

Frequently Asked Questions

Last updated: 2026-05-25 · Reviewed by Nham Vu