Check integer risers and the straight installation length before ordering
A floor height alone is not enough to order a stair.
The first or last rise may change after finishes, and intermediate landings can consume space that a simple rise/run estimate misses.
Reworking fabricated steel or timber is costly, so compare integer riser counts and horizontal installation lengths while requesting quotations.
This calculator enumerates candidates, separates ordinary treads from landings and compares the result with measured space.
This is a Korea-specific dimension planner using the rules checked in 2026.
A dimension found online is not automatically applicable to every home.
Building use, housing-project approval, relevant floor areas, indoor/outdoor classification and overlapping regulations must be established first.
The output is a review sheet for an architect and fabricator, not a permit or structural approval.
Choose an applicable rule or an explicit dimension simulation
Shared and outdoor housing stairs
Check the approved-housing-project scope in Article 3 of the Regulations on Standards for Housing Construction.
Article 16 lists shared stairs with a maximum 180 mm riser, minimum 260 mm going and minimum 1,200 mm clear width.
Outdoor stairs use 200 mm, 240 mm and 900 mm respectively.
For shared outdoor stairs, ask the designer about overlapping requirements instead of selecting the smaller width solely to make the stair fit.
Other indoor residential stairs
Building Act Enforcement Decree Article 48 addresses stairs in buildings with total floor area over 200 m².
Fire/Evacuation Rule Article 15(2)4 requires 1,200 mm indoor width when the relevant upper-storey habitable areas total at least 200 m², or basement habitable areas total at least 100 m².
Upper-storey area runs from the floor immediately above to the top, or to the floor below an upper evacuation floor.
Item 5 sets 600 mm for other indoor stairs.
Total building floor area and the relevant habitable-area sum are different tests.
Items 4 and 5 do not themselves impose universal 180 mm risers and 260 mm goings.
Your riser range and going in these modes are design constraints; other applicable laws may still impose additional requirements.
Unknown applicability pauses the calculation.
Select custom dimension simulation explicitly if you only want geometry under your own constraints.
School, workplace, special-stair, household exceptions and accessibility rules are not automatically evaluated.
Measure finished dimensions consistently
Rise and horizontal length
Measure vertically from the lower finished floor to the upper finished floor.
Do not use ceiling height or sloping stair length.
Available length is the unobstructed horizontal distance in the direction of travel.
Door swings, walls and circulation areas cannot automatically be counted as usable stair space.
Going and clear width
Going means the horizontal advance between successive steps.
Do not double-count nosing projections or overlapping boards.
Available width is the clear space after finishes and rails; design width is the width you intend to provide.
For other indoor stairs over 3,000 mm high, required landings increase the straight clear band to 1,200 mm.
The minimum design riser is your lower search bound, not a statutory minimum.
Supported riser inputs range from 100 to 300 mm.
Equal minimum and maximum values restrict the search to integer counts that match that height exactly.
Enter separately verified bottom and top circulation space as a combined end allowance.
The initial zero allowance does not mean no circulation space is needed.
All dimensions use mm; blank fields remain missing rather than becoming zero.
Risers and separate treads are different counts
The final rise reaches a landing or upper floor
N is the number of vertical rises.
For a single flight finishing at the upper floor, there are N−1 separate ordinary treads.
Across F flights, one tread is omitted at each flight end, giving N−F ordinary treads and F−1 intermediate landings.
Landing depth is then added separately to the horizontal run.
These definitions align the dimension review with a drawing, but do not dictate the fabricator’s bill of materials.
A top platform may be supplied as part of the stair, and one landing may consist of several components.
Ask quotations to identify riser count, ordinary treads, intermediate landings and the upper-floor connection separately.
Landing intervals require integer flight allocation
The normal housing rule calls for landings within each 2,000 mm of rise when total stair rise exceeds 2,000 mm.
Fire/Evacuation Rule Article 15 uses a 3,000 mm threshold and interval, with landings at least 1,200 mm clear.
An exact threshold and a height just above it are different cases.
Household exclusions and exceptions for plant rooms, water-tank rooms and first-floor entrances are not automatically applied.
Dividing total height alone can undercount landings
At a total rise of 3,999 mm and 23 risers, a 12-riser flight exceeds 2,000 mm.
Two flights therefore cannot satisfy that interval, even though the total is below 4,000 mm; three flights are needed.
The calculator first determines the maximum integer risers per flight, then distributes the total as evenly as possible.
A fixed existing landing position or unequal riser heights is outside this model.
Horizontal length formulas and effective dimensions
Dimension formulas
Riser height r = H ÷ N
Ordinary tread count T = N − F
Installation length L = T × going + (F − 1) × landing depth + end allowance
Length shortfall = max(0, L − available length)
Width shortfall = max(0, required width − available width)
Rule mode uses the smaller of your maximum riser and the statutory maximum, and the larger of your going or width and the applicable minimum.
Statutory landing depth and landing width apply only when total rise exceeds the legal height trigger; a voluntary landing below that trigger uses your design dimensions.
A smaller user flight-rise limit is also respected.
Read the effective-dimension line to see any adjustment to the entered values.
Custom simulation applies only your inputs without adding statutory limits.
Inputs use 0.1 mm increments and integer dimension comparisons protect threshold checks.
Displayed riser heights are rounded to three decimals; multiplying that display by the riser count may differ slightly from the total.
The drawing must divide the finished rise evenly, rather than placing rounding differences into the last step.
Step-by-step use
- Confirm use and applicability with a designer, choose the rule, check the confirmation and record a drawing, article, reviewer and date.
- Enter finished vertical rise, available horizontal length and clear width in mm.
Leave unmeasured dimensions blank to keep the result pending.
- Set the riser range, going, design width, flight-rise limit, landing depth and minimum landing count.
Include verified bottom/top circulation allowances separately.
- Compare candidate counts and both length and width shortfalls.
The sketch defaults to the shortest fitting candidate, which is not a comfort or safety ranking.
- Save the TXT review or print it with plans, sections and site photographs.
If you loaded the hypothetical example, replace its confirmation and evidence with actual records.
Worked example: 2,800 mm shared housing stair
Assume 6,000 × 1,200 mm available space, a 150–180 mm riser range, 260 mm going, 1,200 mm landing depth, a 2,000 mm flight-rise limit and zero end allowance.
These are hypothetical inputs, not a site measurement or recommended final design.
Straight stair candidates for a 2,800 mm rise| Risers | Rise mm | Treads | Landings | Length mm |
|---|
| 16 | 175 | 14 | 1 | 4,840 |
| 17 | 164.706 | 15 | 1 | 5,100 |
| 18 | 155.556 | 16 | 1 | 5,360 |
The 16-riser candidate splits into 8 + 8 rises: 14 × 260 + 1,200 = 4,840 mm.
With only 4,800 mm available, even this shortest candidate is 40 mm too long.
Adding 400 mm of end allowance increases its required length to 5,240 mm.
A clear width of 1,100 mm is 100 mm short of the shared-stair width, so adequate length alone does not make it a fitting candidate.
Use the results in design and quotation discussions
When the straight length is insufficient
Do not immediately shorten goings or remove required landings.
Review the stair start, opening and bottom/top circulation while preserving applicable constraints.
A turning alternative requires a separate design; folding this straight result in half does not establish that it fits.
When renovating an older home
New finishes can change the first and last rise.
Separate existing measurements from proposed finish thickness and check width after adding rails.
If several integer counts fit, request comparable dimensioned drawings and quotations for each.
Checks outside this dimension table
- Verify Article 15 provisions including 2,100 mm headroom and rails for stairs or landings over 1,000 mm high in the section drawings.
The calculator does not measure or approve these features.
- Structural loads, connections, fire and evacuation provisions, handrails, slip resistance, accessibility and local requirements need separate review.
A fitting dimension result is not a safety certificate.
- The width model assumes one continuous straight clear band through the landings.
Narrow walls, columns, beams, doors or services may reduce the actual envelope.
- An exact dimensional fit contains no automatic fabrication, measurement or finish tolerance.
Have the designer set any required allowance and record its basis.
Frequently asked questions
Do 16 risers mean 16 treads?
A single flight reaching the upper floor has 15 separate ordinary treads.
With one intermediate landing and two flights, this model counts 14 ordinary treads plus the landing.
Check the fabrication drawing for component quantities.
Can every home use 180 mm and 260 mm?
No.
These are shared-stair values in the Housing Standards and require scope confirmation.
They are not universal statutory values for other indoor or household stairs.
Does exactly 2,000 mm automatically add a landing?
Not under the normal housing height-exceedance trigger alone.
A stricter user flight-rise limit or minimum landing count can still add one.
Can I calculate before confirming the law?
Unknown applicability pauses the review.
Explicit custom dimension simulation shows geometry under your own constraints without making a code-compliance assessment.
Do no fitting candidates prove installation is impossible?
It means the current riser range, landing count and available length or width cannot all be met.
An architect must assess changes to the wider plan.
Should I order the shortest candidate?
Shortest length is only a space-comparison measure.
Obtain a final drawing that also addresses comfort, users, headroom, structure and construction details.
Can I use this with a fixed landing position?
This model balances integer risers across flights.
It does not match fixed openings or landing elevations, which require separate design.
What should accompany the review sheet?
Provide finished rise, widths, bottom/top space, applicable articles and review date, site photographs, plans and sections.
Check the hypothetical-example label and replace it with actual evidence where appropriate.
Official sources, rule dates and the next step
The Korean National Law Information OPEN API was checked directly on 2026-09-25.
Sources are the Fire/Evacuation Rule effective 2025-10-31 (MST 279461), Housing Standards effective 2026-09-08 (MST 289501), and Building Act Enforcement Decree effective 2026-09-18 (MST 288849).
These are the effective dates of the current statute versions, not the original introduction dates of each dimension.
Recheck current provisions and the permitting authority’s guidance when rules change or an earlier permit may involve transitional provisions.
Send the measured inputs, candidates and unresolved checks to the architect and fabricator, then obtain a confirmed dimensioned drawing and written quotation before ordering.
Review candidates with your measurements