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Framing & structure

Stair Rise & Run Calculator with Code Check

Enter the total rise, and the floor length available if you know it, to see how many risers you need, how high each one is, how far the stair runs across the floor and whether it meets the code limits, before you mark the stringer.

Your stair
in
Top of the finished lower floor to the top of the finished upper floor or deck, measured plumb. Leave carpet, rugs and runners out. A bare number is inches: type 107.5, or feet and inches like 8' 11 1/2".
in
Level distance from the front edge of one tread to the front edge of the next, which is also the distance from one riser face to the next.
in
Optional: how much floor the stair may take, measured level from the face of the first riser to the face the stair lands against, which is its total run. The treads share it equally, and the tread run box above then shows the depth each one gets. It is the stair's own run: the floor or landing that R311.7.6 asks for at the bottom and top of a stairway, at least 36 in deep for a straight stair, is not part of it (the top one may be left out on an indoor stair with no door swinging over it). Clear this box to type the tread run again. A bare number is inches; 10' 10" also works.
Starts at the fewest risers that keep each one at 7 3/4 in or less. Add one for an easier climb and a longer stair. Changing the total rise, or clearing this box, sets it back.
in
How far the front of each tread overhangs the riser below it. Enter 0 if the treads have no nosing. A tread run under 11 in needs 3/4 in to 1 1/4 in. The nosing does not change the run.
Edge of the upper floor or deck

The upper floor is the last step of this stair, so its edge is the last nosing. "Same as the treads" means that edge sticks out past the face the stair lands against by the tread nosing, or not at all if the treads have none. "Different" means any other edge, and this tool does not check it. Until you tap one of the two, the result assumes the first.

Headroom and width (optional, in inches)
in
Straight up from the line of the tread nosings to the lowest ceiling, beam or soffit over the stair. A bare number is inches; 6' 8" also works.
in
Between the walls or guards, above handrail height.
Result

    Side view, to scale. The upper floor is the last step, so the stringer carries one tread fewer than there are risers. Total run is from the face of the first riser to the face the stair lands against. The treads and floor finishes are drawn without thickness. The depth of the stringer under the steps is not sized here.
    Options
    RisersRiser, tread, flightRiser heightTreadsTread depthTotal run

    Each row is checked on three limits only: riser height 7 3/4 in or less, tread depth 10 in or more, and one flight rising no more than 12 ft 7 in. The nosing, the upper floor edge, headroom and width are checked in the result above, for the riser count you choose. Tap a row to choose its riser count.

    Mark-out table

    This table gives the marks for equal finished risers and treads, measured along the edge of the stringer; it does not allow for the thickness of the treads or of the floor finishes, or say how to draw or cut the tread and riser lines at each mark or how to fix the stringer, and you must account for those yourself.

    1. Make mark 1 on the top edge of the board, leaving at least one riser height of board below it for the first riser.
    2. Hold the tape at mark 1 and make every other mark at its distance in the first column. Do not walk the square from mark to mark: the exact spacing is , and a rounded spacing adds up.
    MarkAlong the stringer edge from mark 1Top of step above the lower floorRiser face out from the first riser face

    Every figure in the first two columns is worked from one fixed point and rounded to the nearest 1/16 in once.

    Checked against 2021 IRC Section R311.7 for a straight flight. Handrails, guards, landings and the strength of the stringer are not checked. Your jurisdiction may enforce another edition or local amendments.

    Rule: 2021 IRC R311.7 · Tested against 33 worked examples, 3 printed in a published source · How this is worked out →

    Common cases

    Questions people ask

    How many steps do I need for a 108 inch rise?
    At least 14 risers. 108 divided by the 7 3/4 in maximum riser is 13.94, which rounds up to 14, and each riser is then 7.7143 in (≈ 7 11/16 in on a tape). That stair has 13 treads on the stringer, because the upper floor is the last step, and its total run is 130 in at a 10 in tread. With 15 risers each is 7.2 in and the total run is 140 in.
    What is the maximum riser height and minimum tread depth for stairs in a house?
    Under 2021 IRC Section R311.7.5 a riser may be no more than 7 3/4 in high and a tread no less than 10 in deep, measured from the front edge of one tread to the front edge of the next. A tread under 11 in deep also needs a nosing that projects 3/4 in to 1 1/4 in. Your state or city may have amended these figures.
    Why is there one fewer tread than risers?
    This tool lays out a stair whose top riser ends at the upper floor, so the upper floor itself is the last step and needs no tread on the stringer. Its edge then counts as the last nosing, so it should project past the top riser by the same amount as the treads: not at all if the treads have no nosing. If you build with a full tread flush with the upper floor at the top of the stringer, the number and height of the risers are the same but the stair is one tread run longer.
    Do all the steps have to be the same height?
    Nearly. Within one flight the tallest riser may be no more than 3/8 in taller than the shortest, and the deepest tread no more than 3/8 in deeper than the shallowest. Measure the total rise between finished floor surfaces, and do not step a rounded riser height up the stringer: for a 108 inch rise, 13 steps of 7 11/16 in leave the last riser at 8 1/16 in. Measure every mark from one point instead, as the mark-out table on this page does.
    How tall can a stair be before it needs a landing?
    Under 2021 IRC Section R311.7.3 a single flight may rise no more than 12 ft 7 in between floor levels or landings. This tool checks that limit but does not lay out landings.