Stairs for a 3 Foot Deck: Risers, Treads and Stringer Length
Risers
5 at 7.2 in each
36 inches from the ground to the deck surface, 10.5 inch treads, 36 inch wide stairs.
How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Total rise, finished floor to finished floor36 in
- Tread depth you want10.5 in
- Stair width36 in
Risers5 at 7.2 in each
| Total rise | 36 in |
|---|---|
| Number of risers | 5 |
| Riser height | 7.2 in |
| Number of treads | 4 |
| Total run | 42 in (3.5 ft) |
| Stringer length, minimum | 4.61 ft |
| Headroom needed above nosing | 80 in minimum |
The material list this produces
| Stringers, 5 ft | 4 |
|---|---|
| Treads, 36 in | 4 |
| Risers, 36 in | 5 |
Tread depth compared
Deeper treads are more comfortable and eat more floor. Same rise, four tread depths.
| Tread depth | Risers | Total run |
|---|---|---|
| 10 in | 5 at 7.2 in each | 40 in (3.33 ft) |
| 10.5 in | 5 at 7.2 in each | 42 in (3.5 ft) |
| 11 in | 5 at 7.2 in each | 44 in (3.67 ft) |
| 11.5 in | 5 at 7.2 in each | 46 in (3.83 ft) |
What else matters here
Measure the total rise from the finished ground to the finished deck surface, not to the top of the framing. If the landing pad is not poured yet, measure to where its surface will be, because an inch of concrete you forgot is an inch spread across every riser.
Five risers at 7.2 inches each is comfortably inside the 7.75 inch code maximum, and the 42 inch run means the stairs land three and a half feet out from the deck. Check that there is a level landing there at least as deep as the stairs are wide.
The bottom riser is the one people get wrong. It is measured from the landing surface to the top of the first tread, and if the concrete pad is poured after the stringers are cut, that riser ends up short and becomes a trip hazard that no inspector will pass.
What this calculator assumes
- Riser count is the total rise divided by a 7.5 inch target, rounded to a whole number, and then increased by one if that would have put a riser over the code maximum. The rise is then divided evenly among them. Every riser in a flight must be within 3/8 inch of every other one.
- Treads are always one fewer than risers when the top riser lands on the finished floor above.
- The IRC limits are a 7.75 inch maximum riser and a 10 inch minimum tread. Your local code may be stricter, and commercial work certainly is.
Questions people ask
How many steps for a 3 foot deck?
Five risers at 7.2 inches each, with four treads. The top riser lands on the deck surface itself.
How long a stringer for a 3 foot rise?
About 4.6 feet minimum for the cut line, so buy 2x12 stock at 5 feet or longer and cut to fit.
Do 3 foot deck stairs need a handrail?
Usually yes. The IRC requires a handrail on stairs with four or more risers, which this is, and a guard where the walking surface is more than 30 inches above grade.
The stair calculator takes any dimensions you like and hands back the same list.