BuildRight
Stair Stringer Calculator
Divides total rise into even steps and calculates the resulting run — the layout math behind every stair stringer.
Step count, riser height and run for common floor-to-floor heights
Each row uses a 7.5 inch target riser and a 10 inch tread, the calculator defaults. The total rise is divided by the target and rounded to a whole number of steps, then divided back out to give the actual riser height every step must share.
| Total rise (in) | Steps at a 7.5 in target riser | Actual riser height (in) | Total run at 10 in treads (in) | Total run (ft) |
|---|---|---|---|---|
| 24 (low deck) | 3 | 8.00 | 20 | 1.67 |
| 36 (deck to grade) | 5 | 7.20 | 40 | 3.33 |
| 48 (raised deck) | 6 | 8.00 | 50 | 4.17 |
| 60 (split level) | 8 | 7.50 | 70 | 5.83 |
| 84 (low basement) | 11 | 7.64 | 100 | 8.33 |
| 96 (8 ft floor to floor) | 13 | 7.38 | 120 | 10.00 |
| 104 (typical basement) | 14 | 7.43 | 130 | 10.83 |
| 108 (9 ft floor to floor) | 14 | 7.71 | 130 | 10.83 |
| 112 (deep basement) | 15 | 7.47 | 140 | 11.67 |
| 120 (10 ft floor to floor) | 16 | 7.50 | 150 | 12.50 |
Safety critical, and this is layout math rather than code compliance: verify everything against your local building department before cutting a stringer. Most codes cap risers at 7.75 inches and require every riser in a flight to match within 3/8 inch, so the 24 and 48 inch rows, which land on exactly 8.00 inches from a 7.5 inch target, are too tall as shown and need a smaller target riser entered, 6 inches for the 24 inch rise and 6.85 for the 48. Total run is the treads only, one fewer than the number of risers because the upper floor forms the last step, and it does not include the landing space codes require at the bottom. Measure total rise from finished floor to finished floor, including the thickness of any flooring not yet installed.
Risers must be even
Building code requires every riser in a staircase to be the same height (usually within 3/8" of each other) — this calculator finds the number of steps that divides your total rise as evenly as possible into your target riser height.
Check your local code
Riser height, tread depth, and total staircase width are all governed by local building codes, which vary — this calculator does the layout math but doesn't verify code compliance for your specific jurisdiction.
Frequently asked questions
My floor-to-floor height is 108 inches — how many steps do I need?
About 14 steps at a 7.71-inch riser (108 / 14 = 7.71"). That falls within the typical code-compliant range of 7-7.75 inches per riser. Enter your exact total rise above for the precise calculation.
What's the ideal riser height?
Most building codes require risers between 7 and 7.75 inches. The 'ideal' for comfort is about 7-7.5 inches with a 10-11 inch tread. All risers in a staircase must be within 3/8 inch of each other.
How long will my staircase be (total run)?
Total run = number of treads x tread depth. With 14 risers (13 treads, since the top floor is the last step), at 10-inch treads, the total run is 130 inches (about 10 feet 10 inches). Factor this into your floor plan.
Related Home & DIY calculators
Last updated: September 6, 2026