How Many Steps Do I Need for My Deck? (Chart by Height)
Divide the total rise (deck surface to the ground where the stairs land) by 7.75 inches and round up. That's how many risers, or steps up, you need. A 4 foot (48 inch) high deck needs 7 risers of 6 7/8" each and 6 treads. The stair calculator does it for any height and gives the stringer length too.
Steps by deck height
Treads are 10 1/2 inches deep (typical for two 2 × 6 boards or 5/4 decking). Stringer length is to the tip of the cut; buy the next standard board length up.
| Total rise | Risers | Each riser | Treads | Total run | Stringer |
|---|---|---|---|---|---|
| 18 in (1 1/2 ft) | 3 | 6" | 2 | 1' 9" | 2' 3 11/16" |
| 24 in (2 ft) | 4 | 6" | 3 | 2' 7 1/2" | 3' 3 5/8" |
| 28 in | 4 | 7" | 3 | 2' 7 1/2" | 3' 6 1/8" |
| 30 in (2 1/2 ft) | 4 | 7 1/2" | 3 | 2' 7 1/2" | 3' 7 1/2" |
| 36 in (3 ft) | 5 | 7 3/16" | 4 | 3' 6" | 4' 7 5/16" |
| 40 in | 6 | 6 11/16" | 5 | 4' 4 1/2" | 5' 6" |
| 42 in (3 1/2 ft) | 6 | 7" | 5 | 4' 4 1/2" | 5' 7 1/4" |
| 48 in (4 ft) | 7 | 6 7/8" | 6 | 5' 3" | 6' 7 3/16" |
| 54 in (4 1/2 ft) | 7 | 7 11/16" | 6 | 5' 3" | 6' 11" |
| 60 in (5 ft) | 8 | 7 1/2" | 7 | 6' 1 1/2" | 7' 10 7/8" |
| 72 in (6 ft) | 10 | 7 3/16" | 9 | 7' 10 1/2" | 9' 10 13/16" |
| 96 in (8 ft) | 13 | 7 3/8" | 12 | 10' 6" | 13' 2 3/8" |
There's always one fewer tread than risers, because the deck itself is the top step.
Measure the rise properly
Measure from the top of the deck boards straight down to the ground, then check where the bottom step will actually land. Ground usually slopes away from a house, so the rise at the landing spot can be an inch or two more than right under the deck. Run a straight board level out from the deck to the landing point and measure down from there.
Code limits for deck stairs
Most US towns follow the International Residential Code (IRC). Check with your local building department, but the usual rules are:
- Riser height: 7 3/4 inches maximum, and all risers within 3/8 inch of each other.
- Tread depth: 10 inches minimum, measured nosing to nosing.
- Nosing: 3/4 to 1 1/4 inches when treads are under 11 inches deep.
- Width: 36 inches minimum.
- Handrail: required with 4 or more risers, 34 to 38 inches above the nosings.
- Stringer spacing: commonly 16 inches apart for 5/4 decking, and no more than about 12 inches for composite. Check your decking's instructions.
Worked example: 4 foot deck
- Total rise: 48 in
- 48 ÷ 7.75 = 6.19, so round up to 7 risers
- Riser height: 48 ÷ 7 = 6.86 in (6 7/8")
- Treads: 7 − 1 = 6, at 10 1/2 in each = 5' 3" of run
- Stringer: √(48² + 63²) = 6' 7 3/16", so an 8 ft 2 × 12 is enough
Plan for the space: stairs for a 4 foot deck reach more than 5 feet out from the deck, plus a landing at the bottom. If that doesn't fit, turn the stairs with a landing partway down.
Frequently asked questions
How many steps do I need for a 2 foot deck?
A 2 foot (24 inch) high deck needs 4 risers of about 6" each and 3 treads. With 10 1/2 inch treads the stairs run 2' 7 1/2" out from the deck.
How many steps do I need for a 3 foot deck?
A 3 foot (36 inch) high deck needs 5 risers of about 7 3/16" each and 4 treads. With 10 1/2 inch treads the stairs run 3' 6" out from the deck.
How many steps do I need for a 4 foot deck?
A 4 foot (48 inch) high deck needs 7 risers of about 6 7/8" each and 6 treads. With 10 1/2 inch treads the stairs run 5' 3" out from the deck.
How many steps do I need for a 5 foot deck?
A 5 foot (60 inch) high deck needs 8 risers of about 7 1/2" each and 7 treads. With 10 1/2 inch treads the stairs run 6' 1 1/2" out from the deck.
How many steps do I need for a 30 inch deck?
A 30 inch (30 inch) high deck needs 4 risers of about 7 1/2" each and 3 treads. With 10 1/2 inch treads the stairs run 2' 7 1/2" out from the deck.
What is the maximum step height for deck stairs?
Most US codes (the IRC) allow a riser of up to 7 3/4 inches, with treads at least 10 inches deep. All risers in a flight must be within 3/8 inch of each other.
Do deck stairs need a handrail?
Under the IRC, stairs with 4 or more risers need a handrail on at least one side, 34 to 38 inches above the tread nosings. Check your local building department.