Staircase Calculator: Risers, Treads and Concrete
Number of risers = floor-to-floor height ÷ maximum riser, rounded up. A 10 ft (3,048 mm) floor with a 175 mm maximum riser needs 18 risers of 169⅓ mm and 16 treads, in two flights of 9 risers.
This stair calculator also checks the NBC 2016 riser, tread and 12-risers-per-flight limits for your building type, and gives the waist, step and landing concrete in m³.
Calculate risers, treads and concrete
Comfort check: choose your 2R + T band
600–650 mm is this tool’s editable planning band, not an NBC requirement or a safety test.
Risers are rounded up from height ÷ target riser; dog-legged flights share them as evenly as possible. Tread stays at your entered target. Width and slab thickness need the project design.
- Risers / treads (excluding landings)
- 18 / 16
- Actual riser / tread
- 169.333 / 270 mm
- Flight 1
- 9 risers, 8 treads; going 2.16 m
- Flight 2
- 9 risers, 8 treads; going 2.16 m
- Total going, excluding landing
- 4.32 m
- Clear plan envelope, no well or walls
- 3.16 × 2 m
- 2R + T comfort check
- 608.67 mm: inside your band
- Inclined waist length over stepped runs
- 5.0993 m
- Waist concrete
- 0.7649 m³
- Step wedges
- 0.3658 m³
- Intermediate landing
- 0.3 m³
- Modelled concrete subtotal
- 1.4307 m³
NBC 2016 Part 4 checks: riser ≤ 190 mm — within limit; tread ≥ 250 mm — within limit; ≤ 12 risers per flight — within limit. These checks do not establish full compliance.
Waist thickness is perpendicular to the slope. Concrete covers the repeating stepped runs and the intermediate landing only. Add support extensions, junctions, beams and floor landings from drawings. The dog-legged model has adjacent flights with no central well.
Concrete materials calculator · BBS calculator for drawing-based steel
Risers, treads and going: what is counted
Each flight has one fewer tread than risers because the landing or upper floor supplies its last walking surface.
- Take the floor-to-floor height between finished floor levels, in millimetres.
- Divide by the maximum riser you want and round up. The height is then split equally between all risers, with at least two per flight.
- A dog-legged stair splits the risers between two flights as evenly as possible. With an odd count, one flight gets the extra riser and the landing level moves to suit.
- Going per flight = treads × tread depth. The tread stays as you entered it; the tool does not fit the stair into an available length.
The dog-legged plan assumes two flights side by side with no gap (well) between them. Its clear plan is (longer flight’s going + landing depth) × (2 × stair width). Add walls, finishes and any well for the actual opening.
Indian NBC 2016 limits by occupancy
NBC 2016 caps the riser at 190 mm for A-2 private houses (one or two families) and 150 mm for other buildings; the minimum tread is 250 mm for residential and 300 mm for the rest.
| Occupancy | Maximum riser | Minimum tread |
|---|---|---|
| A-2: one or two family private dwelling | 190 mm | 250 mm |
| Other residential: A-1, A-3, A-4 | 150 mm | 250 mm |
| Hotels, assembly, education, institutional, business and other | 150 mm | 300 mm |
Source: NBC 2016 Part 4, clause 4.4.2.4.3.1, page 33. Treads are measured without nosing, and a flight may have at most 12 risers. The code ties 190 mm to A-2, so do not assume it for apartment (A-4) stairs; check the bye-laws your approval follows.
The tool does not check stair width, headroom, landing size, handrails, fire exits or accessibility. Passing these three checks is not compliance.
The 2R + T comfort check is our assumption, not an NBC rule. In the example, 2 × (3,048 ÷ 18) + 270 = 608⅔ mm, inside the 600–650 mm starting band, which you can edit.
How staircase concrete is calculated
Stair concrete = inclined waist + triangular step wedges + intermediate landing, with every dimension in metres.
- Let R be the actual riser, T the tread, W the flight width, w the waist thickness normal to the slope, and N the number of treads.
- The repeating stepped run is N × T long and N × R high, so its inclined length S = N × √(R² + T²).
- Waist volume = S × W × w. Step wedges = N × ½ × R × T × W.
- For the no-well dog-legged layout, intermediate landing volume = (2W) × landing depth × landing slab thickness.
What is left out: a flight rises (N + 1) × R, but the inclined run covers only the N repeating tread modules. Measure the junction at each end and the bearing into beams or floors from the section.
So the result is a subtotal for those parts, not the full pour. Add beams, end zones and floor landings once, without counting floor slab area twice. Then take the total m³ to the concrete calculator for cement, sand and aggregate.
Worked example: 10 ft dog-legged stair
A 10 ft dog-legged stair, 1 m wide, needs about 1.43 m³ (1.430655 m³ unrounded) of concrete for the waist, steps and intermediate landing.
Inputs: 10 ft floor height, 175 mm target riser, 270 mm tread, 1 m flight width, 150 mm waist, and a 1 m deep × 2 m wide intermediate landing, 150 mm thick. Width and slab thickness are example inputs, not structural recommendations.
- Height = 10 × 304.8 = 3,048 mm. Risers = ceil(3,048 ÷ 175) = 18. R = 3,048 ÷ 18 = 169⅓ mm = 127/750 m.
- Two flights: 9 risers and 8 treads each. Each flight rises 1.524 m; each going = 8 × 0.27 = 2.16 m. Total stepped going = 4.32 m.
- The clear plan envelope is (2.16 + 1) × (2 × 1) = 3.16 × 2 m, before walls or a central well.
- Total stepped waist length = 16 × √((127/750)² + 0.27²) = 16√228541 / 1500 ≈ 5.099303 m.
- Waist = (16√228541 / 1500) × 1 × 0.15 = √228541 / 625 ≈ 0.764895 m³.
- Steps = 16 × ½ × (127/750) × 0.27 × 1 = 0.36576 m³.
- Intermediate landing = 2 × 1 × 0.15 = 0.3 m³.
- Subtotal = √228541 / 625 + 0.36576 + 0.3 ≈ 1.430655 m³. Support junctions, floor landings, beams and ordering allowance are additional.
The 169⅓ mm riser passes the A-2 limit of 190 mm but fails the 150 mm limit for other buildings. The 270 mm tread passes the 250 mm residential minimum but not the 300 mm minimum for hotels and the other listed buildings. Each 9-riser flight is within the 12-riser limit.
For reinforcement, enter the engineer’s bar schedule in the BBS calculator. Concrete volume alone does not give steel weight.
Stair calculator FAQs
How many steps do I need for a 10 ft floor height?
18 risers and 16 treads, with a 175 mm maximum riser. 10 ft = 3,048 mm; 3,048 ÷ 175 = 17.4, rounded up to 18 risers of 169⅓ mm. In a dog-legged stair, two flights of 9 risers have 8 treads each; the landing and the upper floor are the last steps.
Is the tread count always one less than the riser count?
One less per flight. A straight 18-riser flight has 17 treads; two flights sharing 18 risers have 16 treads plus an intermediate landing. An 18-riser single flight breaks the NBC 2016 limit of 12 risers per flight.
What are the NBC 2016 riser and tread limits?
Maximum riser 190 mm for A-2 private houses (one or two families) and 150 mm for other buildings. Minimum tread, without nosing, 250 mm for residential buildings and 300 mm for hotels, assembly, educational, institutional, business and other buildings. At most 12 risers per flight. Source: NBC 2016 Part 4, clause 4.4.2.4.3.1.
What does the 2R + T comfort check mean?
Twice the actual riser plus the tread, in mm. The calculator compares it with a 600–650 mm band that you can edit. That band is our planning assumption, not an NBC test.
How is staircase concrete calculated?
Waist = inclined length × width × waist thickness (square to the slope). Steps = ½ × riser × tread × width × number of treads. Add the intermediate landing. Measure end supports, beams and floor landings from the drawings.
Does the calculator design the staircase reinforcement?
No. Width, waist thickness, supports, loads, cover and bars come from the structural design. Use the BBS calculator to total steel from the approved bar details; this page assumes no kg of steel per m³.