How to plan poured concrete steps
- Measure the total rise from the ground where the bottom step will sit to the top of the landing, or to the porch the steps lead up to.
- Enter the largest riser you will accept and the tread depth. The calculator finds the fewest equal risers under your maximum.
- Enter the width of the steps and the depth of the top landing, or 0 if the steps end at an existing porch or slab.
- Order the concrete for the whole job. QUIKRETE's step guide says to mix the entire project at one time.
- Build the side forms from plywood cut to the profile and the riser forms from lumber ripped to the riser height, then brace them well.
How the steps and concrete are calculated
Risers = total rise ÷ maximum riser, rounded up
Riser height = total rise ÷ risers
Treads = risers − 1 (the landing or porch is the top step)
Total run = treads × tread depth + landing depth
Profile area = landing × total rise + tread × riser × risers × treads ÷ 2
Concrete (cu ft) = profile area × width ÷ 1,728
Bags = concrete × (1 + extra) ÷ bag yield, rounded up
Worked example
A back door 21 inches above the patio needs 21 ÷ 7 3/4 = 2.71, rounded up to 3 risers of 7". With 11 inch treads and a 36 inch landing, the steps run out 4' 10" from the house. The side profile is 36 × 21 + 11 × 7 × 3 × 2 ÷ 2 = 987 square inches. At 48 inches wide that is 27.4 cubic feet. With 10% extra, order 30.2 cubic feet (1.12 cubic yards), or 51 bags of 80 lb mix. The same steps up to an existing porch, with no landing, need only 6.4 cubic feet before the allowance.
Code rules for exterior steps
Under the 2021 International Residential Code:
- Risers may be at most 7 3/4 inches high and treads at least 10 inches deep (R311.7.5). Treads under 11 inches need a nosing.
- Stairs need at least 36 inches of clear width (R311.7.1).
- There must be a landing at the top and bottom, as wide as the stairs and at least 36 inches deep (R311.7.6).
- Treads and landings may slope no more than 1 unit in 48, enough to shed water (R311.7.7).
- A flight with four or more risers needs a handrail on at least one side (R311.7.8).
- Open sides more than 30 inches above the ground need a guard (R312.1.1).
Many areas adopt the IRC with local changes, and steps attached to a house may need footings below the frost line. Check with your building department before you pour.
Riser and tread proportions
QUIKRETE's step guide pairs lower risers with deeper treads so the stride stays natural:
| Riser | Tread |
|---|---|
| 4 to 4 1/2 in | 18 to 19 in |
| 5 to 5 1/2 in | 16 to 17 in |
| 6 to 6 1/2 in | 14 to 15 in |
| 7 to 7 1/2 in | 10 to 11 in |
About the defaults
- Maximum riser, 7 3/4 inches: the IRC limit. Lower it for a gentler climb, and deepen the treads to match.
- Treads, 11 inches: inside QUIKRETE's 10 to 11 inch range for 7 inch risers, and deep enough that the IRC needs no nosing.
- Width, 48 inches: the width QUIKRETE says home steps are usually built to. The IRC minimum is 36 inches.
- Landing, 36 inches: the IRC minimum depth, and QUIKRETE's recommended 3 feet.
- Extra concrete, 10%: the top of NRMCA's 4 to 10 percent range.
- Form boards: the narrowest 2x lumber at least as wide as the riser, ripped down to the riser height. A 2 x 8 is 7 1/4 inches wide, so risers taller than that need a 2 x 10.
Frequently asked questions
How many bags of concrete do I need for steps?
Work out the volume of the step profile times the width, add an allowance, and divide by the bag yield. The 3-riser stoop in the example holds 27.4 cubic feet. With 10% extra that is 30.2 cubic feet: 51 bags of 80 lb mix at 0.6 cubic feet each, or 68 bags of 60 lb mix.
How tall should concrete steps be?
The 2021 IRC allows risers up to 7 3/4 inches and requires treads of at least 10 inches. QUIKRETE's step guide pairs 7 to 7 1/2 inch risers with 10 to 11 inch treads, and lower risers with deeper treads. Every riser and tread in a flight must be the same, which is why the calculator splits the rise evenly.
How deep should the landing at the top of concrete steps be?
The IRC requires a landing at the top and bottom of each stairway, at least as wide as the stairs and at least 36 inches deep in the direction of travel. QUIKRETE recommends landings no less than 3 feet deep, with the top landing no more than 7 1/2 inches below the door threshold.
How much extra concrete should I order?
NRMCA, the ready-mixed concrete industry association, advises an allowance of 4 to 10 percent over the plan dimensions for waste, over-excavation and other contingencies, and more for small, scattered placements. The calculator defaults to 10%, the top of that range; change it to match your supplier's advice.
Can I fill concrete steps with rubble to save concrete?
Yes. QUIKRETE suggests filling low areas inside the forms with gravel, broken brick or chunks of concrete block, kept back from the form sides so they do not show through. The calculator assumes solid steps, so 27.4 cubic feet is the most the example needs; fill reduces it.
Should concrete steps slope?
Yes, slightly, so water runs off. The IRC limits the slope of treads and landings to 1 unit in 48, which is 1/4" across a tread 11 inches deep. QUIKRETE recommends a forward pitch of about 1/4 inch per foot, the same thing.