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 estimate step count, riser height, tread going, stair angle, and stringer length. It also provides a simplified headroom estimate and a basic materials takeoff for planning.
How the Stair Calculator Works
- Riser count: We choose a whole-number riser count based on your preferred riser, then recompute the exact riser so the total rise matches the floor height.
- Flights: For L and U stairs, total risers are split across flights (landings don’t add rise).
- Tread going: Starts from your preferred value and trims if the available run is tight.
- Angle: \( \theta = \arctan(\text{riser} / \text{going}) \), reported in degrees.
- Stringer length: \( \sqrt{\text{rise}^2 + \text{run}^2} \) per flight.
- Headroom: A simplified estimate based on opening length and stair slope—does not account for framing depth; verify on site.
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 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 landings, reducing footprint while keeping comfortable risers and goings.
Frequently Asked Questions
How many steps do I need for a given floor height?
A quick estimate is floor height ÷ preferred riser height, rounded to a whole number. This calculator chooses a whole-number riser count and recalculates the exact riser so the total rise matches your floor-to-floor height.
What’s a comfortable riser and going?
Many residential stairs target risers around 170–190 mm (6.5–7.5 in) and tread going around 250–300 mm (10–11.5 in). Comfort and code requirements vary—always verify local standards.
What’s Blondel’s rule (2R+G)?
Blondel’s rule is a comfort guideline: 2 × riser + going ≈ 600–640 mm (about 23.6–25.2 in). Values outside this band can feel too steep or too shallow. This calculator reports a 2R+G check.
How do I calculate stringer length?
Stringer length per flight is the sloped distance: √(rise² + run²). The calculator computes each flight’s rise/run from its assigned risers and treads, then returns the stringer length.
Related Lumber & Framing Calculators
Estimates only. Always verify on site and follow local building codes or consult a qualified professional.
Accuracy & Review
Reviewed by: Liam Santos
Liam reviews our decking, lumber, and board foot calculators to confirm accurate framing takeoffs, dimensional lumber calculations, and practical assumptions. He focuses on ensuring estimates reflect real-world building layouts and material usage.
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See: Methodology · Data Sources · Review Board
Important Estimate Disclaimer
These estimates are for general planning purposes only and should not be used as structural design guidance. Actual lumber quantities depend on span limits, load requirements, material grade, and building code compliance.
See our Methodology and Data Sources for reference information.
Structural framing components should be verified against current code requirements before construction.