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Stair Dimensions Calculator

Home stairs can have risers up to 7¾ in and treads at least 10 in deep under the IRC. Enter your floor-to-floor height to get the number of steps, riser height, tread depth and total run.

Units

= 109 in · 276.9 cm

Check against
Risers
15

Auto: fewest within IRC

tread depth, nosing to nosing

IRC minimum

floor depth above the stair, for headroom

Joists + subfloor

Optional: the floor length you have

IRC R311.7 · 9 ft 1 in floor to floor

Within IRC limits — 2R + T 24 9/16 in: a comfortable stride

15 risers at 7¼ in14 treads at 10 in

Total run 11 ft 8 in · 36.0°

Riser ≤ 7¾ in
7¼ in (Meets)
Tread ≥ 10 in
10 in (Meets)
Flight ≤ 12 ft 7 in
9 ft 1 in (Meets)
2R + T 24–25 in
24 9/16 in (Comfortable)
Stair side view drawn to scaleSide view to scale: 15 risers of 7¼ in and 14 treads of 10 in, rising 9 ft 1 in over a run of 11 ft 8 in. The upper floor opening is at least 10 ft 3⅞ in long for 6 ft 8 in of headroom.6 ft 8 in9 ft 1 in11 ft 8 in10 ft 3⅞ in
Nosing lineHeadroomDrawn to scale
Stringer (diagonal)
About 14 ft 9 7/16 in
Angle
36.0°; 30–35° feels easiest
Opening for 6 ft 8 in headroom
At least 10 ft 3⅞ in long
Width and handrail
36 in wide; rail 34–38 in high

How the numbers work
  • Risers and treads: one straight flight, all risers equal (floor to floor ÷ risers); the upper floor is the top step, so there is one tread fewer than risers. Auto picks the fewest risers the code allows.
  • IRC R311.7 (homes): risers up to 7¾ in, treads at least 10 in, no more than ⅜ in difference in a flight, 6 ft 8 in of headroom, 36 in of width, a landing every 12 ft 7 in of rise, and a handrail 34–38 in high on flights of 4 or more risers.
  • IBC 1011 (other buildings): risers 4–7 in, treads at least 11 in, a landing every 12 ft, shown for comparison.
  • 2R + T: a rule of thumb, not code. Twice the riser plus the tread near 24–25 in matches a natural stride.
  • Stairwell opening: (headroom + floor depth) × tread ÷ riser, measured back from the top nosing; at least 6 ft 8 in of headroom above the nosing line.

A planning aid, not a construction drawing. Your local code, its amendments and your inspector decide; winders, spiral stairs and landings follow extra rules.

Reference table

Stair Height Code: IRC Limits for Home Stairs

The 2021 IRC R311.7 limits for stairs in houses. Many places adopt them with local changes, so check yours.

DimensionIRC limitMetricSectionGood to know
Riser heightMax 7¾ in19.7 cmR311.7.5.1Leading edge to leading edge
Tread depthMin 10 in25.4 cmR311.7.5.2Nosing to nosing, level
Difference in a flightMax ⅜ in0.95 cmR311.7.5.1Tallest vs shortest riser or tread
HeadroomMin 6 ft 8 in203.2 cmR311.7.2Straight up from the nosing line
WidthMin 36 in91.4 cmR311.7.131½ in at one handrail, 27 in at two
Nosing¾–1¼ in1.9–3.2 cmR311.7.5.3Not needed with 11 in treads
Flight riseMax 12 ft 7 in383.5 cmR311.7.3Higher than that needs a landing
Landing depthMin 36 in91.4 cmR311.7.6Straight runs, in the direction of travel
Handrail height34–38 in86.4–96.5 cmR311.7.8.1Needed with 4 or more risers

Measured without carpet or runners. Metric figures are conversions at 2.54 cm per inch; the code prints its own rounded millimeters.

Standard Stair Height: Steps for Common Floor Heights

The fewest risers the IRC allows for each floor-to-floor height, with 10 in treads. Measure from finished floor to finished floor.

Floor to floorMetricRisersRiser heightTreadsTotal runGood to know
8 ft243.8 cm137⅜ in1210 ft2R + T 24¾ in: comfortable
8 ft 6 in259.1 cm147 5/16 in1310 ft 10 in2R + T 24 9/16 in: comfortable
9 ft274.3 cm147 11/16 in1310 ft 10 in15 risers of 7 3/16 in feel easier
9 ft 6 in289.6 cm157⅝ in1411 ft 8 in16 risers of 7⅛ in feel easier
10 ft304.8 cm167½ in1512 ft 6 in2R + T 25 in: comfortable
10 ft 6 in320 cm177 7/16 in1613 ft 4 in2R + T 24 13/16 in: comfortable
11 ft335.3 cm187 5/16 in1714 ft 2 in2R + T 24 11/16 in: comfortable
12 ft365.8 cm197 9/16 in1815 ft20 risers of 7 3/16 in feel easier
13 ft396.2 cm217 7/16 in2016 ft 8 inOver 12 ft 7 in: add a landing

Riser heights are rounded to the nearest 1/16 in; lay out the stringer from the total rise. Total run counts treads only, not the landing at the top.

Step Dimensions Standards: IRC vs IBC vs Comfortable

Code limits for homes and for other buildings, next to a rule-of-thumb range for stairs that feel easy to climb.

DimensionIRC (homes)IBC (other buildings)ComfortableGood to know
Riser heightMax 7¾ in4–7 in6½–7½ inLower risers mean more steps
Tread depthMin 10 inMin 11 in10–11 inNosing to nosing
2 × riser + treadNot in codeNot in code24–25 inAbout one natural stride
AngleMax about 37.8°Max about 32.5°30–35°Set by the riser and tread limits
HeadroomMin 6 ft 8 inMin 6 ft 8 in7 ft 4 in–7 ft 7 inAbove the nosing line
WidthMin 36 inMin 44 in—IBC: 36 in under 50 people
Flight riseMax 12 ft 7 inMax 12 ft—Then a landing
Difference in a flightMax ⅜ inMax ⅜ inAs even as you canUneven steps trip people

IRC R311.7 and IBC 1011 (2021 editions). The comfortable column is a rule of thumb from stair-layout teaching notes, not a code requirement.

Plan a Stair That Meets Code and Feels Right

Total rise and total runSide view of one straight flight between a lower floor and an upper floor. Total rise runs from floor surface to floor surface; total run runs from the first riser to the last.Total riseTotal runUpper floor
Illustrative diagram

Count the Steps From Floor to Floor

Measure the total rise from finished floor to finished floor, then use the fewest risers that stay within the 7¾ in limit. A 9 ft rise needs 14 risers of 7 11/16 in, and there is always one tread fewer than risers.

Try a 9 ft Floor-to-Floor
Riser, tread depth and nosingClose-up of three steps. The riser is measured from the top of one tread to the top of the next; the tread depth from one nosing to the next; the nosing is the front edge that overhangs the riser below.RiserTread depthNosing
Illustrative diagram

Check Home or Commercial Limits

Houses follow the IRC: risers up to 7¾ in and treads at least 10 in, measured nosing to nosing. Offices, shops and other buildings follow the IBC: risers of 4–7 in and treads of 11 in or more. Switch codes to see one rise checked both ways.

Switch to IBC Limits
The comfort rule: two risers plus a treadTwo risers and one tread of a step are highlighted, then laid out flat in a row. Together they come to about one natural stride. This is a rule of thumb, not a code requirement.Laid out flat2 risers+ tread≈ one strideA rule of thumb, not code
Illustrative diagram

Make the Stair Feel Easy

Within the limits is not always comfortable. A rule of thumb says twice the riser plus the tread should land near 24–25 in, about one stride. At 9 ft with 14 risers that comes to 25 7/16 in; one more riser brings it to 24⅜ in.

Try 15 Risers on a 9 ft Stair
Headroom and the stairwell openingA stair climbing through an opening in the floor above. A dashed nosing line joins the front edges of the treads; headroom is measured straight up from that line to the underside of the floor, and it sets how long the opening must be.Nosing lineHeadroomOpeningFloor above
Illustrative diagram

Keep Headroom Over the Stair

You need 6 ft 8 in of headroom above the nosing line all the way up, so the floor above needs an opening. Its length depends on the floor depth and the slope: a 9 ft 1 in rise with a 10 in floor needs at least 10 ft 3⅞ in.

Enter Your Floor Depth

How to Measure and Plan a Stair

A tape measure, a level and the calculator above are all it takes.

  1. 1

    Measure the total rise

    Measure from the finished floor at the bottom to the finished floor at the top. If the flooring is not down yet, add the thickness of what you plan to lay.

  2. 2

    Set the code and treads

    Pick IRC for a house or IBC for other buildings, then enter your tread depth. If the stride line says the stair feels steep, add a riser and check again.

  3. 3

    Check space and headroom

    Enter the floor length you have and the depth of the floor above. Confirm the opening and landing sizes with your building department before you cut any stringers.

Riser, tread depth and nosingClose-up of three steps. The riser is measured from the top of one tread to the top of the next; the tread depth from one nosing to the next; the nosing is the front edge that overhangs the riser below.RiserTread depthNosing
Illustrative diagram
Plan your stair

When Stair Dimensions Matter

  • Finishing a basement

    Basement stairs are often the steepest in the house. Check the riser height and the headroom before you frame a new ceiling over them.

  • Building deck or porch steps

    The IRC covers stairs that serve a deck or porch. With 4 or more risers you need a handrail, and open risers more than 30 in up must stop a 4 in ball.

  • Moving furniture upstairs

    A stair only 36 in wide under 6 ft 8 in of headroom can stop a large sofa at the turn. Measure the stair and the furniture before you buy.

FAQ

Questions About Stair Dimensions

There is no single standard. Stair-layout guides aim for risers of about 6½–7½ in and treads of 10–11 in, and the IRC caps risers at 7¾ in. A 9 ft floor-to-floor rise takes 14 or 15 risers, depending on how steep you want the stair.

In homes, the IRC allows risers up to 7¾ in, measured between the leading edges of the treads, and the tallest riser in a flight may not exceed the shortest by more than ⅜ in. The IBC limits other buildings to 7 in, with a 4 in minimum.

The IRC requires treads at least 10 in deep, measured nosing to nosing, plus a ¾–1¼ in nosing unless treads are 11 in or deeper. The IBC requires 11 in. Carpet and runners do not count toward either figure.

Usually, yes. People asking about tread height or step height mean the riser: the vertical distance from one tread to the next. Under the IRC that is 7¾ in at most. Tread depth is the flat part you step on, front to back.

At least 6 ft 8 in under both the IRC and the IBC, measured straight up from the line joining the tread nosings. Stair-layout guides suggest 7 ft 4 in to 7 ft 7 in for comfort. The opening in the floor above must be long enough to keep it.

The IRC asks for 36 in of clear width above the handrail, and 31½ in at and below it with one handrail or 27 in with two. The IBC asks for 44 in, or 36 in where the stair serves fewer than 50 people.

The IRC limits one flight to 12 ft 7 in of vertical rise and the IBC to 12 ft; above that, add a landing. A straight-run landing must be at least 36 in deep. A full 12 ft 7 in flight takes at least 20 risers.

No. It works out one straight flight from published code figures and rules of thumb, so you can plan and compare options. It is not a construction drawing. Winders, spiral stairs and landings add rules, and your local code, its amendments and your inspector decide.