Stair Calculator
Calculate riser height, tread depth, stringer length and angle for any staircase
Calculate By
Total Rise (cm)
cm
Floor-to-floor height
Target Riser Height (cm)
cm
Steps will be rounded to nearest whole number
Tread Depth (cm)
cm
Ideal: 23–30 cm (building code)
Stair Dimensions
Number of Steps
—
Riser Height
—
Tread Depth
—
Total Run
—
Stringer Length
—
Stair Angle
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Stair Design Basics
Building codes typically require: riser height 15–20 cm (6–8 inches), tread depth 23–30 cm (9–12 inches). A common rule of thumb: 2 × riser + tread ≈ 63–65 cm. The stringer (the diagonal side board) length is calculated using the Pythagorean theorem: √(rise² + run²).
Comfortable stairs have a stair angle of 30–35°. Below 30° is very gradual (good for steep slopes), above 45° is very steep and may not meet code. Always consult local building codes before construction, as requirements vary by region.
lightbulb Example
Floor-to-floor height: 270 cm
1Target riser: 18 cm → 15 steps
2Riser: 270/15 = 18 cm ✓
3Run: 25 × 14 = 350 cm
✓ Stringer: 449 cm, angle: 37.6°