Stair Dimensions: Riser Height, Tread Depth, and Nosing Overhang

Standard Stair Sizes at a Glance

For homes built under the International Residential Code (IRC), the figures that matter most are these. They are the same in the 2018 and 2021 editions.

Commercial and multifamily buildings follow the International Building Code (IBC), which is stricter: a maximum riser of 7 inches, a minimum of 4 inches, and a minimum tread of 11 inches.

Codes are adopted and amended locally, so confirm the figures with your building department before you build or alter a staircase.

Riser Height

The riser height is the vertical distance from the top of one tread to the top of the next. Under the IRC it is capped at 7 3/4 inches, measured vertically between the leading edges of adjacent treads. Most comfortable residential stairs land between 7 and 7 1/2 inches.

The IRC states only a maximum. The IBC sets a 4 inch minimum. In practice what matters most is consistency: a riser that differs from its neighbors by even a fraction of an inch is what trips people, which is why the code caps variation at 3/8 inch within a flight.

Tread Depth

Tread depth is measured horizontally from the front edge of one tread (the nosing) to the front edge of the next. The IRC minimum is 10 inches. The IBC minimum is 11.

A deeper tread is easier and safer to use. A shallow tread leaves less room for your foot, which is why code requires a nosing projection when the tread is under 11 inches.

What the 7-11 Rule Means

The common comfort rule is a riser of about 7 inches and a tread of about 11 inches. That pairing feels natural for most people and sits within both residential and commercial limits. Another rule of thumb says twice the riser plus the tread should land between about 24 and 25 inches. Both are guides, not code.

Nosing Overhang

The nosing is the part of the tread that projects past the riser. Under the IRC, where risers are solid and the tread is shallower than 11 inches, the nosing must project at least 3/4 inch and no more than 1 1/4 inches. The edge itself should be rounded or beveled with a radius no greater than 9/16 inch.

This matters for flooring, because a stair nose adds material to the front edge. Choosing a nose with a large overhang or thick profile can push the nosing past the allowed projection. For a deeper look at nosing types, see stair nosing: what it is and which type you need.

How to Measure Your Own Stairs

• Riser height: measure from the top of one tread to the top of the next. Check every step, not just one.
• Tread depth: measure from the front of one nosing to the front of the next, horizontally.
• Total rise: measure from the finished lower floor to the finished upper floor, then divide by the number of risers.

The number of treads is always one fewer than the number of risers, because the upper floor acts as the last tread.

Here is a worked example. A staircase with a total rise of 108 inches divided by a target of 7 inches gives 15.4, so you round to 16 risers of 6 3/4 inches each. That staircase has 15 treads, and at 10 inches each the total run is 150 inches.

For flooring and stair-nose measurements, see the measurement guide and how to measure for LVP stair nosing. If any of the terms here are unfamiliar, parts of a staircase defines them.

What Happens When You Add Flooring

Covering stairs with new flooring changes the numbers, and this is the part most guides skip. Every tread surface rises by the thickness of the new covering, including adhesive. If the floors at the top and bottom of the stairs are not changing, the first riser gets taller and the last riser gets shorter by that same thickness.

Here is how it plays out with a 1/4 inch covering. The first riser grows by 1/4 inch and the last riser shrinks by 1/4 inch. On its own that is inside the 3/8 inch limit. But a thicker plank, an underlayment, or a heavy adhesive layer can push the difference past 3/8 inch.

If the floor at the top and bottom is also being replaced with a similar thickness, the changes largely cancel out, so it is worth checking all three together.

Two other changes are worth knowing about:

• Building out a riser or extending the nosing can reduce the measured tread depth, so remeasure nosing to nosing after the change
• A new stair nose can change the projection, so check it against the 3/4 to 1 1/4 inch range

If you are renovating an existing staircase rather than rebuilding it, local rules on what triggers a code review vary. A call to the building department answers it.

Other Stair Dimensions People Ask About

Using This for a Flooring Project

If you are planning to cover your stairs, the measurements to take before you order are the riser height, tread depth, step width, and whether each step is open on a side. A correct set of measurements also makes a custom stair nose quote faster. The installation guide and the guide to installing LVP on stairs cover the next steps.