Staircase Calculator – Fast, Accurate Stair Design for Builders & DIYers
This free staircase calculator helps you size straight, L-shaped, and U-shaped stairs. Enter your floor-to-floor height and the available run for each flight, and the calculator will determine the optimal riser count, riser height, tread going, stair angle, and stringer length. It also provides a simple headroom check and a handy materials takeoff for treads, risers, stringers, handrail, and balusters.
How the Stair Calculator Works
- Riser count: We round to the nearest whole number from your preferred riser height, then recompute the exact riser.
- Tread going: Starts from your preferred value and is trimmed if the available run is tight.
- Angle: \( \theta = \arctan(\text{riser} / \text{going}) \), reported in degrees for comfort and compliance checks.
- Stringer length: \( \sqrt{\text{rise}^2 + \text{run}^2} \) per flight (useful for ordering stock).
- Headroom: We compare clearance at the opening edge against your minimum headroom setting.
Typical Targets & Tips
- Comfortable risers: many builders aim for ~170–190 mm (6.5–7.5 in).
- Comfortable going: often ~250–300 mm (10–11.5 in).
- Headroom: set a minimum around 2.0–2.1 m (78–82 in); verify local codes.
- Blondel rule: a good comfort check is \(2 \times \text{riser} + \text{going} \approx 600–640\,\text{mm}\) (23.6–25.2 in).
Stair Types Covered
Straight stairs are quick to build and fit narrow spaces. L-shape stairs turn a corner with a landing, improving safety and layout. U-shape stairs reverse direction with two landings, reducing the footprint while maintaining comfortable risers and goings.
Frequently Asked Questions
How many steps do I need for my floor height?
Divide your floor-to-floor height by a comfortable riser (e.g., 175 mm / 7 in) and round to the nearest whole number. The calculator does this automatically and rechecks comfort and headroom.
What is a comfortable stair angle?
Most residential stairs fall around 30–38°. Very steep stairs are harder to navigate; shallow angles need more run.
What does “available run” mean?
It’s the horizontal distance you can dedicate to each flight, measured from the first nosing to the landing or to the edge of the upper-floor opening for a straight stair.
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Estimates only. Always verify on site and follow local building codes or consult a qualified professional.