Reference chart
Stair Rise & Run Chart & Calculator
Find your total rise in the chart for the riser count, riser height, run and stringer length at a 10½-inch tread and the IRC 7¾-inch maximum. The calculator below takes an exact rise, your tread depth and the commercial limit.
Risers, riser height and total run by floor-to-floor height
| Total rise | Risers | Riser height | Treads | Total run | Stringer | Angle | 2R + T |
|---|---|---|---|---|---|---|---|
| 24″ (2′ 0″) | 4 | 6″ | 3 | 31.5″ | 39.6″ | 29.7° | 22.5 |
| 30″ (2′ 6″) | 4 | 7.5″ | 3 | 31.5″ | 43.5″ | 35.5° | 25.5 |
| 36″ (3′ 0″) | 5 | 7.2″ | 4 | 42″ | 55.3″ | 34.4° | 24.9 |
| 42″ (3′ 6″) | 6 | 7″ | 5 | 52.5″ | 67.2″ | 33.7° | 24.5 |
| 48″ (4′ 0″) | 7 | 6.86″ | 6 | 63″ | 79.2″ | 33.1° | 24.2 |
| 54″ (4′ 6″) | 7 | 7.71″ | 6 | 63″ | 83″ | 36.3° | 25.9 |
| 60″ (5′ 0″) | 8 | 7.5″ | 7 | 73.5″ | 94.9″ | 35.5° | 25.5 |
| 66″ (5′ 6″) | 9 | 7.33″ | 8 | 84″ | 106.8″ | 34.9° | 25.2 |
| 72″ (6′ 0″) | 10 | 7.2″ | 9 | 94.5″ | 118.8″ | 34.4° | 24.9 |
| 78″ (6′ 6″) | 11 | 7.09″ | 10 | 105″ | 130.8″ | 34° | 24.7 |
| 84″ (7′ 0″) | 11 | 7.64″ | 10 | 105″ | 134.5″ | 36° | 25.8 |
| 90″ (7′ 6″) | 12 | 7.5″ | 11 | 115.5″ | 146.4″ | 35.5° | 25.5 |
| 96″ (8′ 0″) | 13 | 7.38″ | 12 | 126″ | 158.4″ | 35.1° | 25.3 |
| 102″ (8′ 6″) | 14 | 7.29″ | 13 | 136.5″ | 170.4″ | 34.8° | 25.1 |
| 108″ (9′ 0″) | 14 | 7.71″ | 13 | 136.5″ | 174.1″ | 36.3° | 25.9 |
| 114″ (9′ 6″) | 15 | 7.6″ | 14 | 147″ | 186″ | 35.9° | 25.7 |
| 120″ (10′ 0″) | 16 | 7.5″ | 15 | 157.5″ | 198″ | 35.5° | 25.5 |
| 126″ (10′ 6″) | 17 | 7.41″ | 16 | 168″ | 210″ | 35.2° | 25.3 |
| 132″ (11′ 0″) | 18 | 7.33″ | 17 | 178.5″ | 222″ | 34.9° | 25.2 |
| 138″ (11′ 6″) | 18 | 7.67″ | 17 | 178.5″ | 225.6″ | 36.1° | 25.8 |
| 144″ (12′ 0″) | 19 | 7.58″ | 18 | 189″ | 237.6″ | 35.8° | 25.7 |
Your numbers
IRC minimum 10″
7¾″ IRC; 7″ commercial (IBC)
drops the bottom of the stringer
Risers
14
13 treads
Riser height
7 11/16″
7.714″ · within code
Total run
136 1/2″
13 × 10.5″
Stringer
174 1/16″
36.3° · 2×12 throat OK
Risers = ceil(108 ÷ 7.75) = 14; riser = 108 ÷ 14 = 7.714″. Cut the first riser 6 11/16″ (riser − tread thickness) so every finished step matches. Comfort check 2R + T = 25.9 (aim for 24–25).
Questions
How do I calculate the number of stair risers?
Divide the total rise (finished floor to finished floor) by the maximum riser, 7¾ inches under the IRC, and round up. Then divide the total rise by that count for the actual riser height. A 108-inch rise is 108 ÷ 7.75 = 13.9, so 14 risers of 7.71 inches. Treads are always one fewer than risers.
What are the code limits for stairs?
IRC R311.7: maximum riser 7¾ inches, minimum tread depth 10 inches, no more than ⅜ inch variation between the largest and smallest riser or tread, minimum 36 inches wide, 6 feet 8 inches of headroom. Commercial stairs under the IBC are 7-inch maximum risers and 11-inch minimum treads.
What is a comfortable rise and run?
Twice the riser plus the tread should be between 24 and 25 inches: 7 and 11, 7¼ and 10½, 7½ and 10. Steeper than 7¾ and 10 is a ladder; shallower than 6 and 12 feels like a ramp. The chart's riser column shows how a 10½-inch tread pairs with each rise.
How long a board do I need for the stringer?
The stringer length is the hypotenuse of total rise and total run, shown in the chart. Add about a foot for the top and bottom cuts and buy the next even length of 2×12. A 2×12 notched for a 7¾ × 10½ stair keeps just over 5 inches of throat, which is the usual minimum; use a 2×14 or an attached cleat design for deeper treads.
Why cut the bottom riser shorter?
Because the tread thickness gets added to every step except the floor below the first riser. Cutting the first riser short by the tread thickness makes every finished rise equal, which is what the ⅜-inch rule measures.
Charts are computed from the formulas and code figures stated on the page (International Residential Code limits where cited). They are planning and take-off numbers, not engineering: species, grade, span tables and local amendments govern anything structural. Confirm with your inspector before you cut.