The standard stair rise and run is a 7 to 7.75 inch riser with a 10 to 11 inch tread. There is no single standard because the code sets limits rather than a figure: the model IRC caps the riser at 7.75 inches and puts a floor of 10 inches under the tread, and everything between those is legal. What actually decides your riser is the rise of your building divided by a whole number of steps.
The limits on the standard stair rise and run, and who changes them
- Maximum riser: 7.75 in under the model IRC
- Minimum tread: 10 in, measured nosing to nosing
- Uniformity: the tallest riser may not exceed the shortest by more than 3/8 in, and the same for treads
- Headroom: 6 ft 8 in, measured from the nosing line
- One flight: no more than 147 in of rise before a landing
States amend these. Michigan, for one, allows a riser of 8.25 inches and a tread of 9. That is why the calculator on this site asks for your limits rather than assuming the model numbers, and why a rule of thumb read on the internet is worth less than the page your building department publishes.
The old comfort rules still work
Two rules that predate the code
2 × riser + tread = 24 to 25 in riser + tread = 17 to 18 in
Carpentry rules of thumb, not code, and they agree with the code in the middle of the range
Run the legal extremes through them and you can see where a stair stops being pleasant to climb:
- 7 by 11: 25 and 18. The classic comfortable stair, and it needs the most floor space
- 7.5 by 10: 25 and 17.5. Comfortable, tighter run
- 7.75 by 10: 25.5 and 17.75. Legal under the model code, and at the steep end of what the old rules like
A shallow tread with a tall riser is the combination that trips people, because the foot lands with less of it supported just as the climb gets steeper. If you have the floor space, spend it on the tread.
See what your rise divides into
Why your riser is never a round number
Rise is not something you choose. A 108 inch floor to floor divided by the 7.75 maximum is 13.9 steps, which is not a number of steps, so the flight has 14 risers of 7.71 inches. A 110 inch rise gives 7.86, over the limit, so it takes 15 risers of 7.33. The riser height falls out of the division, and the only lever you have is the step count. That is why the standard stair rise and run is a range rather than a single number.
This is also how the uniformity rule is satisfied without effort. Divide the rise equally between whole steps and every riser in the flight is identical, so the 3/8 inch tolerance never comes into it. The tolerance exists for stairs built to a nominal riser and finished with whatever is left over at one end, which is the failure it was written to catch.
Frequently asked
A riser of 7 to 7.75 inches with a tread of 10 to 11. The model IRC caps the riser at 7.75 and sets a 10 inch minimum tread, so the standard is a range rather than a single figure.
Twice the riser plus the tread should land between 24 and 25 inches. It is a carpentry rule of thumb rather than code, and it agrees with the code through the middle of the legal range.
No. The tallest riser may not exceed the shortest by more than 3/8 inch. Dividing the total rise equally between a whole number of steps makes them identical, which is the simplest way to comply.