Stair Tread & Riser Calculator – Steps for Any Rise | CalcLoft
Find out exactly how many risers and treads you need for any floor-to-floor rise — actual riser height in inches, total run in feet and US code limits.
How to calculate stair risers and treads
Measure the total rise — the vertical distance from the top of the lower finished floor to the top of the upper finished floor. Then divide it by your target riser height. About 7 inches is the comfortable, code-safe default:
Number of risers = total rise ÷ target riser, rounded up
Rounding up keeps every riser at or below your target. Divide the total rise by the final count to get the actual riser height, then plan one fewer tread than risers, because the upper floor (the top landing) replaces the last tread:
Number of treads = risers − 1 · Total run = treads × tread depth
Example: an 8 ft floor-to-floor rise is 96 in. 96 ÷ 7 = 13.7, rounded up to 14 risers at 96 ÷ 14 = 6.86 in (6-7/8 in) each. With 10 in treads you need 13 treads, and the run is 13 × 10 = 130 in (10.8 ft).
How many stairs for a 96, 105, 110 or 120 inch rise?
The table below uses a 7 in design riser with 10 in treads — divide the rise by 7 and round up, exactly as the calculator above does:
| Total rise | Risers (steps) | Actual riser | Treads | Total run |
|---|---|---|---|---|
| 96 in (8 ft) | 14 | 6.86 in (6-7/8 in) | 13 | 10.83 ft (130 in) |
| 105 in (8 ft 9 in) | 15 | 7.00 in | 14 | 11.67 ft (140 in) |
| 110 in (9 ft 2 in) | 16 | 6.88 in (6-7/8 in) | 15 | 12.50 ft (150 in) |
| 120 in (10 ft) | 18 | 6.67 in (6-11/16 in) | 17 | 14.17 ft (170 in) |
For a 120 in (10 ft) rise, rounding up from a 7 in target gives 18 risers at about 6-2/3 in. Many builders instead build 17 risers at about 7-1/16 in — still under the 7-3/4 in maximum and closer to the comfortable 7 in spacing — when the stair opening and headroom allow. Both counts are legal; the calculator picks the conservative rounded-up count so no riser exceeds your target.
Riser and tread sizes that pass US code
The International Residential Code (IRC) is the default for US homes. Commercial stairs follow the International Building Code (IBC), which is stricter:
| Dimension | Limit |
|---|---|
| Riser height — residential (IRC) | 4 in minimum, 7-3/4 in maximum |
| Riser height — commercial (IBC) | 7 in maximum |
| Tread depth — residential (IRC) | 10 in minimum |
| Tread depth — commercial (IBC) | 11 in minimum |
| Riser variation within one flight | No more than 3/8 in between the tallest and shortest riser |
The traditional comfort rule of thumb is 2R + T ≈ 25 in: twice the riser height plus one tread depth should land near 24–25 in. With 7 in risers and 10 in treads you get 2 × 7 + 10 = 24 in — right in the band. The calculator reports your own 2R + T check with every result.
How to measure total rise for stairs
Measure from the top of the finished floor below to the top of the finished floor above, at the same point vertically — drop a plumb line or use a laser through the stair opening. For a stair with an intermediate landing, treat the landing as the top of the lower flight and measure each flight's rise separately; this tool covers one straight flight.
Remember that the total run is the tread portion only. Add space for nosing overhang, the lower-floor landing and code headroom (6 ft 8 in minimum over the stair) when you lay out the opening, and see the stringer guide below before cutting the framing.
Related guides
Stair calculator FAQ
What is the standard stair riser height?
In US homes a riser can be anywhere from 4 in to 7-3/4 in (IRC). 7 in is the standard design target, and roughly 6-3/4 to 7-1/4 in feels best to most people. Keep every riser within about 3/8 in of the others — uneven risers cause most stair trips. Commercial stairs (IBC) are capped at 7 in.
How do I count the number of steps for a staircase?
Count risers, not treads: divide the total rise by your target riser (about 7 in) and round up. For a 96 in rise that is 96 ÷ 7 = 13.7 → 14 risers, and because the upper floor is the last landing you need 13 treads. When in doubt, count the number of vertical rises — that is always the riser count.
What is the 2R + T rule for stairs?
2R + T is a comfort rule of thumb: twice the riser height plus one tread depth should come to about 25 in (most guides accept 24–25 in). A 7 in riser with a 10 in tread gives 2 × 7 + 10 = 24 in — comfortable. If 2R + T runs well above 25 in the stair feels steep; well below, it feels long and shallow. The rule complements, but does not replace, the code maximums in the table above.
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