Does your step pass the 7-3/4 in test? Under the 2021 IRC, that is the tallest riser allowed, and 10 in is the shallowest tread. A third rule limits how much one step may differ from the next.
Under the 2021 IRC, a riser can be no taller than 7-3/4 in, a tread no shallower than 10 in, and no riser or tread in a flight may differ from the others by more than 3/8 in. Divide the total rise by 7.75, round up, then split the rise evenly. Local code governs.
The Two Limits and the 3/8 Inch Rule
Under the 2021 IRC, a riser may be no taller than 7-3/4 in (196 mm) and a tread no shallower than 10 in (254 mm). Both are measured in a set way, so measure the same way on your own forms.
A riser is measured vertically between the leading edges of adjacent treads. A tread is measured horizontally between the vertical planes of the foremost projections of adjacent treads, at right angles to the tread’s leading edge.
Under the 2021 IRC, a flight also has a uniformity rule. The tallest riser may not exceed the shortest by more than 3/8 in (9.5 mm), and the deepest tread may not exceed the shallowest by more than 3/8 in.
Take four risers measured at 7.50, 7.50, 7.50 and 7.90 in. The tallest minus the shortest is 7.90 – 7.50 = 0.40 in. That is more than 3/8 in, which is 0.375 in, so the flight fails the uniformity rule under the 2021 IRC. The 7.90 in riser also tops the 7.75 in limit.
The Concrete Stairs Calculator takes a rise and a run as inputs but does not check them against code. Those limits come from your building code.
How Many Risers Does a Total Rise Need?
Divide the total rise by 7.75 in and use the result as the fewest risers that can work, then divide the total rise by the whole number you pick. A flight with a landing at the top has one fewer tread than risers.
- Total rise 30 in. 30 / 7.75 = 3.87, so at least 4 risers. Then 30 / 4 = 7.5 in each, which is under 7-3/4 in (7.75 in). With a landing at the top there are 3 treads. At the 10 in minimum the run is 3 x 10 = 30 in; with 11 in treads it is 3 x 11 = 33 in.
- Total rise 42 in. 42 / 7.75 = 5.42, so at least 6 risers. Then 42 / 6 = 7.0 in each. With 5 treads of 11 in, the run is 5 x 11 = 55 in.
Under the 2021 IRC, a flight may not rise more than 12 ft 7 in between floor levels or landings. That is 12 x 12 + 7 = 151 in.
What Do Tread Depth and Nosings Require?
Under the 2021 IRC, a tread must be at least 10 in deep, and a nosing projection must be at least 3/4 in and no more than 1-1/4 in. No nosing projection is required where the tread is 11 in or deeper.
The nosing edge has its own limit under the 2021 IRC: a radius of curvature no greater than 9/16 in, or a bevel no greater than 1/2 in. The greatest nosing projection in a flight may not exceed the smallest by more than 3/8 in.
Risers must be vertical, or sloped from the underside of the nosing at no more than 30 degrees from vertical. Where a flight has open risers, the openings more than 30 in above the floor or grade below must not pass a 4 in sphere, under the 2021 IRC.
Back to the 30 in example. With 11 in treads the run is 33 in, and under the 2021 IRC no nosing projection is required at that depth. With treads at the 10 in minimum, the 3/4 to 1-1/4 in projection range applies.
Where Do Landings, Width and Handrails Come In?
Under the 2021 IRC, a floor or landing is required at the top and bottom of each stairway, with an exception for interior stairs. A landing must be at least as wide as the flight it serves, and on a straight run its depth in the direction of travel must be at least 36 in.
Stairway width has two figures under the 2021 IRC. The clear width must be at least 36 in above handrail height and below the headroom height. At and below handrail height it must be at least 31-1/2 in with a handrail on one side, or 27 in with handrails on both sides. Headroom must be at least 6 ft 8 in.
A handrail is required on at least one side of each flight with four or more risers, under the 2021 IRC. Its height is 34 to 38 in, measured vertically from the sloped plane adjoining the tread nosing. Both examples above qualify: the 30 in flight has 4 risers, and the 42 in flight has 6.
Your inspector decides how these apply to your steps. This article does not cover guards.
How Much Should the Walking Surface Slope?
Under the 2021 IRC, treads and landings may slope no steeper than 1 unit vertical in 48 units horizontal. The code calls that a 2 percent slope.
QUIKRETE’s project sheet says steps should pitch forward about 1/4 in per foot for drainage. That pitch is 1/4 / 12 = 1/48, the same ratio as the 2021 IRC maximum.
Take a landing 4 ft deep. At 1/4 in per foot, the fall across it is 4 x 0.25 = 1.0 in.
For a stepped ramp walkway on a long slope, the same sheet limits the riser to 6 in and the slope to 1/8 to 1/4 in per foot. A plain ramp is a different job, and the concrete ramp calculator covers it.
How Does the 2021 IRC Compare With QUIKRETE’s 2006 Chart?
The 2021 IRC sets limits, while QUIKRETE’s 2006 project sheet gives a chart of riser and tread pairs for home steps. The sheet adds that riser and tread size ultimately depends on use, and that risers and treads must be uniform in a flight.
| Source | Riser | Tread | Uniformity | Landing |
|---|---|---|---|---|
| 2021 IRC (a code) | At most 7-3/4 in | At least 10 in | Within 3/8 in across a flight | At least 36 in deep on a straight run; at least as wide as the flight |
| QUIKRETE project sheet (2006, a recommendation) | 4 to 7-1/2 in, by chart band | 10 to 19 in, paired with the riser | Must be uniform in a flight (no figure given) | At least 3 ft deep; a landing should divide flights over 5 ft high; top landing no more than 7-1/2 in below the door threshold |
| Concrete Stairs Calculator FAQ | Commonly 6 to 7.75 in | Commonly 10 to 11 in | Not stated (local code sets the limits) | Not stated |
QUIKRETE’s chart pairs a 4 to 4-1/2 in riser with an 18 to 19 in tread, a 5 to 5-1/2 in riser with 16 to 17 in, a 6 to 6-1/2 in riser with 14 to 15 in, and a 7 to 7-1/2 in riser with 10 to 11 in.
The chart is older, from 2006, and it is a recommendation. The 2021 IRC is a code. Both are shown here as written; this article does not rank one above the other.
Why Do Local Code and the Inspector Decide?
The IRC is a model code, so your jurisdiction adopts its own edition and can amend it. Local code governs, and the edition differs by place. Every code figure above is from the 2021 edition.
QUIKRETE’s Concrete Mix data sheet lists steps, ramps, walkways, slabs and patios among its uses. For footings, see the concrete footing calculator.
Once your risers and treads are set, enter them in the stairs estimator. For other pours, the concrete calculator covers them.
Keep reading: how wide a walkway should be, rebar sizes and what the numbers mean and how deep footings should be.
Related calculator: Concrete Formwork Calculator.
More: structural concrete calculators or all construction guides.
FAQs About Concrete Step Dimensions
How high can a riser be?
Under the 2021 IRC, a riser can be no more than 7-3/4 in (196 mm), measured vertically between the leading edges of adjacent treads.
How deep must a tread be?
Under the 2021 IRC, a tread must be at least 10 in (254 mm) deep, measured horizontally between the vertical planes of the foremost projections of adjacent treads.
How much can risers differ in one flight?
Under the 2021 IRC, the tallest riser in a flight may not exceed the shortest by more than 3/8 in. The same 3/8 in limit applies to tread depths and nosing projections.
Do I need a nosing on my steps?
Under the 2021 IRC, a nosing projection of at least 3/4 in and no more than 1-1/4 in is required, except none is required where the tread is 11 in or deeper.
How wide should concrete steps be?
Under the 2021 IRC, a stairway needs at least 36 in of clear width above handrail height. QUIKRETE’s 2006 sheet says home steps are usually built 48 in wide or as wide as the door and walk.
When do I need a handrail?
Under the 2021 IRC, each flight with four or more risers needs a handrail on at least one side, set 34 to 38 in above the sloped plane adjoining the tread nosing.
How steep can the walking surface slope?
Under the 2021 IRC, treads and landings may slope no steeper than 1 unit vertical in 48 horizontal, a 2 percent slope. That equals 1/4 in per foot, QUIKRETE’s drainage pitch for steps.
Sources and Further Reading
References Used in This Article
- International Code Council, 2021 International Residential Code, Chapter 3, Section R311.7 (Stairways), accessed 2026-10-19.
- QUIKRETE, Concrete Steps and Ramps project sheet, accessed 2026-10-19.
- QUIKRETE, Concrete Mix 1101 data sheet (revised October 2022), accessed 2026-10-19.
Code figures are from the 2021 IRC; your local code and inspector decide what applies. This is not a design for a particular stair. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated 2026-10-19.
Shakeel Muzaffar is the Founder and Editor-in-Chief, with over 15 years of experience in digital publishing and online tool development. He oversees editorial quality and formula verification to ensure accurate, practical, and easy-to-use calculators.