Staircase design calculator
Enter the floor-to-floor height, your going (tread) and a target riser, and get the number of risers and treads, the actual riser height, total run and slope — with the 2R + T comfort rule checked instantly.
Built around common NBC / IS stair guidance for Nepal — flagging risers over 190 mm and goings under 250 mm. A planning-level tool, computed in your browser.
Stair parameters
Finished-floor to finished-floor vertical rise the stair must climb.
Horizontal depth of each step. NBC suggests ≥ 250 mm; 280 mm is comfortable for homes.
Preferred step height. The number of risers is rounded to fit, then the actual riser is back-calculated.
Risers needed
18 risers
17 treads · actual riser 161 mm
Comfort check
Pass
Actual riser
161 mm
Tread (going)
280 mm
Total run
4,760 mm
Slope
29.9°
| Risers | round(2,900 ÷ 165) = 18 |
| Actual riser (R) | 2,900 ÷ 18 = 161 mm |
| Treads | 18 − 1 = 17 |
| Total run | 17 × 280 = 4,760 mm |
| Slope | atan(161 ÷ 280) = 29.9° |
| Comfort 2R + Ttarget 550–650 mm | 2 × 161 + 280 = 602 mmOK |
| Riser ≤ 190 mmNBC max riser | 161 mmOK |
| Tread ≥ 250 mmNBC min going | 280 mmOK |
A planning-level layout. Real designs must also resolve headroom (≈ 2,000–2,100 mm clear), landing lengths, handrail height, nosing, fire-escape width and structural depth per the building code and local bylaws. Riser, going and comfort limits here follow common NBC / IS stair guidance and are indicative — verify the rule that applies to your occupancy and the current code edition.
From floor height to a step you can climb
A stair divides a fixed vertical rise into equal risers; the going sets how far you step forward, and together they decide whether the stair feels comfortable or steep.
Count the risers
Divide the floor-to-floor height by your target riser and round to a whole number, then back-calculate the actual riser so every step is identical.
Lay out the run
Treads are one fewer than risers (the top riser meets the upper floor). Multiply treads by the going to get the total run in plan.
Check comfort & code
Test 2R + T against 550–650 mm, the riser against ≤ 190 mm and the going against ≥ 250 mm, and read off the slope in degrees.
Staircase design, answered
How do I calculate the number of risers and treads?+
Divide the floor-to-floor height by your target riser height and round to the nearest whole number — that is the number of risers. The number of treads (steps you walk on) is always one less than the number of risers, because the top riser lands at the upper floor level. This calculator then back-calculates the actual riser as floor-to-floor height ÷ number of risers so every step is identical.
What is the 2R + T comfort rule?+
The stepping or 'comfort' formula is 2R + T, where R is the riser height and T is the going (tread depth), both in millimetres. A comfortable stair keeps 2R + T in roughly the 550–650 mm range — it reflects the natural relationship between how high and how far a person steps. Values outside this band tend to feel either too steep and tiring or too shallow and shuffling.
What are the maximum riser and minimum tread for a staircase?+
Common NBC / IS stair guidance for residential stairs keeps the riser at or below about 190 mm and the going (tread) at or above about 250 mm; public and institutional stairs are usually more generous (lower risers, deeper goings). This tool flags your stair if the actual riser exceeds 190 mm or the going is under 250 mm. Always confirm the limit for your occupancy class and the current code edition.
How is the stair slope (pitch) worked out?+
The slope is the angle the stair line makes with the horizontal: slope = atan(riser ÷ going), converted to degrees. Comfortable private stairs are typically around 30–37°. Above about 42° a stair feels steep and approaches ladder territory; the slope here updates live as you change the riser and going.
What is the total run (going) of a staircase?+
The total run is the horizontal distance the staircase occupies in plan, measured across the treads: total run = number of treads × going. Use it to check the stair fits the available floor space before adding landings — remember the last riser lands at the upper floor, so there is no tread at the very top.
Does this calculator replace a structural or code check?+
No. It sizes the riser, tread, run and slope and screens them against common comfort and NBC/IS limits, but a real design must also resolve headroom, landings, handrails, nosing, fire-escape width, structural depth and your local building bylaws. Treat the outputs as indicative and have a qualified engineer or architect confirm the final design.
Sources & data note
Riser, going and slope follow standard stair geometry (risers = round(height ÷ target riser), actual riser = height ÷ risers, total run = treads × going, slope = atan(riser ÷ going)). The 2R + T = 550–650 mm comfort band and the ≤ 190 mm riser / ≥ 250 mm going limits reflect common NBC / IS residential stair guidance and are indicative — verify the values for your occupancy class and the current code edition before construction.