Stairs for a 4 Foot Deck: Risers, Treads and Stringer Length
Risers
7 at 6.86 in each
48 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 floor48 in
- Tread depth you want10.5 in
- Stair width36 in
Risers7 at 6.86 in each
| Total rise | 48 in |
|---|---|
| Number of risers | 7 |
| Riser height | 6.86 in |
| Number of treads | 6 |
| Total run | 63 in (5.25 ft) |
| Stringer length, minimum | 6.6 ft |
| Headroom needed above nosing | 80 in minimum |
The material list this produces
| Stringers, 7 ft | 4 |
|---|---|
| Treads, 36 in | 6 |
| Risers, 36 in | 7 |
Tread depth compared
Deeper treads eat more floor. Same rise, four tread depths.
| Tread depth | Risers | Total run |
|---|---|---|
| 10 in | 7 at 6.86 in each | 60 in (5 ft) |
| 10.5 in | 7 at 6.86 in each | 63 in (5.25 ft) |
| 11 in | 7 at 6.86 in each | 66 in (5.5 ft) |
| 11.5 in | 7 at 6.86 in each | 69 in (5.75 ft) |
What else matters here
Six risers would divide 48 inches into 8 inch steps, which is over the 7.75 inch code maximum, so this lands on seven risers at 6.86 inches instead.
Seven risers puts the stairs 63 inches out from the deck, and the stringer cut line is about 6.6 feet, which the material list rounds up to 7.
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 4 foot deck?
Seven risers at 6.86 inches each, with six treads. Six risers would be 8 inches each, which exceeds the IRC maximum.
Why not 6 risers for 48 inches?
Because 48 divided by 6 is exactly 8 inches, and the IRC caps a residential riser at 7.75 inches. Adding a riser brings it to 6.86, inside the limit.
What size stringer for a 4 foot rise?
The cut line is about 6.6 feet, and the material list rounds that up to a 7 foot stringer.
The stair calculator takes any dimensions you like and hands back the same list.