Stair calculator: how many steps do I need?
A free metric stair calculator with National Building Code figures. No sign-up, and nothing leaves your browser.
Your stair
Type the total rise, floor to floor, and your stair appears here.
One fewer or one more?
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Marks from the lower floor
| Step | Height above the lower floor | Level distance from the first tread's edge |
|---|
Your stair against the NBC figures for private stairs
industryoversight.ca/tools/stair-calculator/
How the stair calculator works
You start with one measurement: the height from the finished floor at the bottom to the finished floor at the top. The rest of the stair falls out of it.
Divide that height by the tallest step you'll allow and round up. That's the fewest risers that fit. A 2,730 mm basement stair under the National Building Code's 200 mm private-stair maximum comes to 13.65. That rounds up to 14 risers, and 2,730 divided by 14 is exactly 195 mm. There's always one tread fewer than there are risers, because the upper floor is the last step.
Multiply the treads by the run, the level distance from one nosing to the next, and you have the floor the stair needs: 13 runs of 260 mm take 3,380 mm. The diagonal from the floor to the top edge is the square root of the rise squared plus the run squared, about 4,345 mm here. Don't buy a stringer that long. It needs extra for the cuts at both ends.
Marking is where stairs go wrong. Over 14 risers, 2,750 mm comes to 196.43 mm a step, and a tape reads that as 196. Step off 196 thirteen times and you're at 2,548 mm, so the last riser comes out at 202: over the maximum, and 6 mm taller than its neighbour where the Code allows 5. We mark each step from the floor and round it on its own. The marks run 196, 393, 589 and on up to 2,750, and no two risers differ by more than a millimetre.
Imperial tapes have a trap of their own. "About 8 inches" is 203.2 mm, already over 200, and even 7 7/8 in is 200.025 mm, a hair over. Switch to feet and inches and the exact millimetres stay underneath, so rounding for the screen never changes your count.
Two more numbers keep the ends right. Type your tread thickness and you get the bottom riser cut: with 38 mm treads on 195 mm risers, the stringer's first step is cut to 157 mm, so the first finished step matches the rest. And if the flooring isn't down yet, add it under More details. Fifteen millimetres of flooring on the upper floor turns a 2,790 mm rise from 14 risers into 15.
Every code line comes from the National Building Code's published figures for the kind of stair you picked, with the edition, the article and the date we read them. The lines show where your stair sits against those figures. The building official who inspects it makes the call.
Who this is for
- Homeowners finishing a basement or putting a stair down to a new basement suite, who know the floor-to-floor height and want the riser count before buying stringers.
- Anyone replacing the steps from a back door or a deck, where the handrail question turns on how many risers there are.
- Anyone holding a contractor's drawing that says "14 risers at 195" who wants to check it against their own floors.
- Carpenters who want the marks and the bottom cut in millimetres, on a phone, on site.
Homeowner questions about stair rise and run
How many stairs do I need for an 8 foot ceiling?
Count from the total rise, not the ceiling. The rise is the ceiling height plus everything in the floor above it: joists, subfloor and finished flooring. Say that comes to 2,770 mm. Under the NBC's 200 mm private-stair maximum that's 14 risers of 197.9 mm and 13 treads, and at a 255 mm run the stair takes 3,315 mm of floor. Measure yours. Floor depths vary too much to guess.
What is the maximum stair riser height in Canada?
Under the National Building Code it's 200 mm for a private stair and 180 mm for a public one, measured nosing to nosing (Table 9.8.4.1, the same in the 2020 and 2025 editions). There's a minimum too: 125 mm. The risers in a flight also have to match, within 5 mm of each neighbour and 10 mm overall. An 8 inch riser is 203.2 mm, so it's already over.
What is the minimum tread depth for stairs in Canada?
The NBC sets the run, measured nosing to nosing: at least 255 mm and at most 355 mm on a private stair, at least 280 mm on a public one (Table 9.8.4.2). The tread depth is the board itself, nosing to riser. It has to be at least the run and no more than the run plus 25 mm (Sentence 9.8.4.2.(2)), so a 255 mm run takes a board 255 to 280 mm deep.
How many steps can you have without a handrail?
On a stair serving one dwelling unit, two risers indoors and three outdoors (Sentence 9.8.7.1.(3)). Add one more and the NBC wants a handrail on at least one side. That exemption covers a single dwelling unit only, so a stair shared by a home and its secondary suite, or any public stair, needs a handrail at any number of risers. Guards along an open side are a separate rule (Article 9.8.8.1).
How do I measure the total rise of stairs?
Measure from the top of the finished floor at the bottom to the top of the finished floor at the top, at the spot where the stair will land. For steps off a deck, run a straight board level off the deck edge and measure down to where the bottom step will sit, pad included. Flooring not down yet? Measure what's there and add the flooring under More details.
How do you calculate stair stringer length?
Square the total rise, square the total run, add them and take the square root. A 2,730 mm rise with 14 treads at 260 mm runs 3,640 mm, and the diagonal comes to exactly 4,550 mm. That's the line from the floor at the foot to the top edge, not the board to buy. The stringer needs extra length for its end cuts, so buy long and lay it out from the marks.
How many risers before a landing?
The NBC doesn't count risers. It caps the height of one flight at 3.7 m (Article 9.8.3.3). At the full 200 mm a riser, 18 fit: 3,600 mm is fine and 3,800 mm isn't, however short you make the steps. The Code generally wants a landing at both ends of a flight, with specific exceptions at doors and exterior stairs (Article 9.8.6.2). A finished floor or level pad can count as a landing. Interior flights outside a dwelling unit need at least 3 risers (Article 9.8.3.2).
What does the Ontario Building Code say about stair rise and run?
Ontario's code is the NBC 2020 as changed by the province's own amendment document (O. Reg. 163/24). The province sends that document on request. We haven't seen it, so we won't promise its stair figures. What we did read: under the older code, for permits applied for from January 1, 2022, Ontario set private stairs at 125 to 200 mm of rise and 255 to 355 mm of run (O. Reg. 88/19). Your building department has today's figures.
Stair rise and run code in Canada: the National Building Code figures
The National Building Code is a model code. Provinces and territories adopt it as written or with their own changes, on their own schedule, which is why every figure here carries its edition. Read side by side, the 2020 and 2025 editions give the same stair numbers:
| What | Private stair | Public stair | Where, 2020 and 2025 |
|---|---|---|---|
| Rise, nosing to nosing | 125 to 200 mm | 125 to 180 mm | Table 9.8.4.1 |
| Run, nosing to nosing | 255 to 355 mm | at least 280 mm, no maximum | Table 9.8.4.2 |
| Tread depth, nosing to riser | the run to the run plus 25 mm | the same | Sentence 9.8.4.2.(2) |
| Risers in one flight | within 5 mm of each neighbour, 10 mm overall | the same | Sentence 9.8.4.4.(1) |
| Runs in one flight | within 5 mm of each neighbour, 10 mm overall | the same | Sentence 9.8.4.4.(3) |
| Height of one flight | at most 3.7 m | the same | Article 9.8.3.3 |
| Handrail | from 3 risers indoors and 4 outdoors on a stair serving one dwelling unit; at any count otherwise | at any number of risers | Sentences 9.8.7.1.(1) and (3) |
| Clear height over the stair | at least 1,950 mm; 1,850 mm under beams and ducting in secondary suites | at least 2,050 mm | Article 9.8.2.2 |
| Width | at least 860 mm for exit stairs, at least one stair between each floor level within a dwelling unit, and exterior stairs serving one dwelling unit | at least 900 mm for residential stairs; other occupancies need the greater of 900 mm or 8 mm per occupant | Article 9.8.2.1 |
Private or public is the Code's own split, and you choose it in the calculator. Note (1) to Table 9.8.4.1 calls a stair private when it serves "single dwelling units", "houses with a secondary suite including their common spaces", or a garage that serves either. Everything else, service stairs aside, is public. The catch is the secondary suite. The Code counts a two-unit house only when both units are registered under the same title, so a stair shared by two strata-titled units is public: 180 mm risers at most, and a handrail at any count.
In the NBC, run and tread depth are two different numbers. The run is the step you mark on the stringer. The tread depth is the board, nosing to riser (Figure A-9.8.4.-B). Some stair guides online call the run the tread depth, and a 255 mm "tread" bought as a 255 mm board leaves no room for a nosing.
The step from a house into its attached garage counts as part of the house (Article 9.8.1.2). Unless it's a required exit stair, a top or bottom riser beside a sloping garage floor or driveway may vary across the stair by up to 1 in 12 (Sentence 9.8.4.4.(2)).
Sources and last checked
- Stair figures: National Building Code of Canada 2020, First Printing, Volume 2, Division B, Section 9.8 and its Notes, read from the Government of Canada Publications copy on October 7, 2026. The 2025 edition, first printing, same sections, we read on October 4, 2026 and again on October 7, 2026. We cite figures and article numbers only. The Code's text belongs to the National Research Council of Canada.
- Millimetres and inches: an inch is 1/36 of a yard and a yard is 0.9144 m, so an inch is exactly 25.4 mm (Weights and Measures Act, Schedule II).
- Ontario: O. Reg. 163/24 and O. Reg. 88/19 on e-Laws, read October 7, 2026. We haven't seen Ontario's amendment document to the NBC 2020.
- Data: stair-code-limits, NBC rows, version of October 7, 2026.
More tools for your project
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