Staircase Calculator
Design a comfortable staircase: number of steps, riser, tread and the floor space it will occupy.
Inputs
150–175 mm is comfortable at home
Formula
- Number of risers = floor height ÷ riser height (rounded)
- Actual riser = floor height ÷ number of risers
- Comfort rule: 2 × riser + tread = 600–640 mm
A staircase always has one more riser than treads. Divide the floor-to-floor height by a comfortable riser (about 165 mm), round to a whole number, then recalculate the exact riser so all steps are equal — unequal steps are a trip hazard. The comfort rule 2R + T between 600 and 640 mm tells you whether the stair will feel natural to climb.
Step-by-step calculation
- 1
Risers
height ÷ preferred riser
18
- 2
Actual riser
height ÷ risers
169.3 mm
- 3
Going
treads × tread depth
4,760 mm
Worked example
- 1Floor height 10 ft = 3,048 mm; at 165 mm that is 18.5, so use 18 risers.
- 2Actual riser = 3048 ÷ 18 = 169 mm, with 17 treads of 280 mm.
- 3Going = 17 × 280 = 4,760 mm ≈ 15.6 ft of floor length.
Tips
- Keep headroom of at least 2.1 m above every step.
- Split long flights with a landing after 12–15 steps.
Frequently asked questions
What is a comfortable step height?
150–175 mm at home. Above 190 mm the stair feels steep and tiring.
How many steps for a 10 ft floor?
Usually 17 or 18 risers of about 170 mm each.
Why is there one less tread than riser?
The top landing acts as the last tread, so treads are always risers minus one.
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