Concrete steps calculator
Enter your steps, get the concrete you need.
How much concrete do I need for steps?
For solid steps, each step is a block from the ground to its top. 3 steps with 7-inch risers, 11-inch treads and 48 inches wide need 12.83 cubic feet — 0.48 cubic yard, before extra.
How many bags is that?
An 80-lb bag of concrete mix yields about 0.6 cubic foot and a 60-lb bag about 0.45 (Quikrete). The calculator rounds up.
What riser and tread sizes are allowed?
Under the International Residential Code (R311.7.5), risers may be at most 7¾ inches and treads at least 10 inches. Check your local code, which may differ.
How do I include a landing?
Enter the landing depth at the top; it is counted at the full height of the stairs.
How much extra should I order?
A margin for spillage and uneven ground is common — the calculator adds the percentage you enter.
What riser and tread proportions does QUIKRETE recommend?
Taller risers go with shorter treads. QUIKRETE’s chart pairs 4 to 4½ inch risers with 18 to 19 inch treads, 5 to 5½ with 16 to 17, 6 to 6½ with 14 to 15, and 7 to 7½ with 10 to 11; all must be uniform within a flight. Under the 2021 IRC the limits are a 7¾ inch maximum riser (R311.7.5.1) and a 10 inch minimum tread (R311.7.5.2), with no more than ⅜ inch variation in a flight.
How wide should steps and landings be?
QUIKRETE says steps for homes are usually 48 inches wide, or at least as wide as the door and walk they serve. It recommends a landing for any flight more than 5 feet high, landings at least 3 feet deep, and a top landing no more than 7½ inches below the door threshold. A landing is solid concrete too, so it adds a lot of volume.
Do I need the full amount if I fill the inside?
The calculator assumes every step is solid concrete down to the ground, the most you would need. QUIKRETE says low areas inside the forms may be filled with gravel, broken brick or concrete block, which reduces the mix needed; keep the filler back from the form sides. In that case treat the calculated volume as an upper limit.
How the volume is worked out
The calculator treats each step as a solid block that runs from the ground up to the surface of that step. With a riser height r, a tread depth t and a width w, the first step is r high, the second 2r, and so on, so the blocks have volumes r·t·w, 2r·t·w, 3r·t·w. Added together for n steps, the volume is r·t·w·n(n + 1) ÷ 2, divided by 1,728 to convert cubic inches to cubic feet and by 27 for cubic yards. A top landing of depth d adds d·(n·r)·w, because it stands at the full height of the stairs. The extra percentage is applied to the total, and bags are rounded up at about 0.6 ft³ per 80-lb bag and 0.45 ft³ per 60-lb bag (QUIKRETE Concrete Mix No. 1101 data sheet).
Worked example
Take the three-step flight from the first answer. The blocks are 7, 14, 21 inches high, so the volume is 7 × 11 × 48 × (1 + 2 + 3) = 22,176 in³, or 12.83 ft³. With the calculator’s default 10% extra that becomes 14.12 ft³ (0.52 yd³), which takes 24 bags of 80-lb mix or 32 bags of 60-lb mix. Four steps with 7½ inch risers and 10 inch treads need 20.8 ft³, or 22.9 ft³ with extra. Adding a 36 inch deep top landing to the three-step example raises the total to 33.8 ft³ without extra, about 63 80-lb bags with it, since the landing is 21 inches thick.
Common mistakes
The commonest is leaving out the landing, which can be more than half of the concrete in a short flight. Second is entering the total rise instead of the single riser height: the field wants one riser, in inches, and the number of steps separately. Third, forgetting that the 6 inch compacted gravel or sand base QUIKRETE describes is not part of the concrete volume. Fourth, choosing dimensions that fail the local code, which may amend the IRC limits above. Finally, ask the building department whether your steps need a footing; the calculator counts only the steps themselves.
Sources: QUIKRETE project guide “Concrete Steps and Ramps” (proportions chart, width, landings, fill, base) and QUIKRETE Concrete Mix No. 1101 data sheet (80-lb and 60-lb yields); 2021 International Residential Code sections R311.7.5.1 and R311.7.5.2 (riser and tread limits). Related: concrete calculator, stair calculator, gravel calculator and cubic yard calculator.