How Much Concrete for Stairs?
A basic 4 step concrete stair, 36 inches wide, needs roughly 0.65 cubic yards of concrete, about 30 bags of 80 lb mix, once you add a landing or extra width the volume climbs fast because each lower step carries the weight of every step above it. Below is the formula, worked examples by step count and width, bag counts, rebar and stringer notes, and a calculator that does the math for your exact stairs.
Key takeaways
- Volume (cubic yards) = width x tread x riser x N(N+1)/2, all in feet, divided by 27, plus 10% waste.
- Four standard steps at 36 inches wide need about 0.65 cubic yards, roughly 30 bags of 80 lb mix.
- A landing or porch pad adds volume fast: 3 steps plus a 4 foot landing can jump from 0.4 to over 1.2 cubic yards.
- One cubic yard takes about 45 bags of 80 lb concrete, and most stair pours stay under that, so bags are usually cheaper than a ready-mix minimum.
- Ready-mix concrete runs about 125 to 195 dollars per cubic yard delivered in 2026, before short-load fees on small orders.
The formula to calculate concrete for stairs
Concrete stairs are poured solid, so each lower step sits under the full stack of steps above it. The volume is not just one step multiplied by the step count, because step 1 only has one riser of concrete beneath it while step 5 has five.
The formula that captures this is width x tread x riser x N(N+1)/2, with width, tread and riser all converted to feet, then divided by 27 to get cubic yards. N is the number of steps, and N(N+1)/2 is the sum of 1 through N, which accounts for the growing depth under each step.
Cubic feet = Width(ft) x Tread(ft) x Riser(ft) x [N x (N+1) ÷ 2]Cubic yards = Cubic feet ÷ 27Always add 5 to 10% for waste, since the subgrade under a stair pour is rarely perfectly even. For the exact number with your own step count, width, rise and run already worked out, use the concrete stairs calculator.
Concrete needed by number of steps (worked examples)
Using a standard 7 inch riser and 11 inch tread, which meets most residential codes, here is how volume scales with step count and stair width. Figures include a 10% waste allowance.
| Steps | 36 in wide (cu yd) | 36 in wide (bags) | 48 in wide (cu yd) | 48 in wide (bags) |
|---|---|---|---|---|
| 3 | 0.39 | 18 | 0.52 | 24 |
| 4 | 0.65 | 30 | 0.87 | 39 |
| 5 | 0.98 | 44 | 1.31 | 59 |
| 6 | 1.37 | 62 | 1.83 | 82 |
Notice how a 6 step run needs more than triple the concrete of a 3 step run, not double, because of the cumulative N(N+1)/2 term. Wider stairs scale in direct proportion to width, so a 60 inch stair is 25% more concrete than a 48 inch stair with the same step count.
Adding a landing or porch pad
Most entry stairs end at a landing or porch slab, and that flat section often uses more concrete than the steps themselves. A landing is calculated as a simple slab: depth x width x thickness, exactly like the concrete slab calculator handles for patios and pads.
As a real-world reference, 3 steps with no landing run about 0.38 cubic yards (18 bags), but adding a 4 foot deep landing at the same width pushes the total to roughly 1.22 cubic yards, about 55 bags. Measure the landing separately, then add its volume to the stair volume before ordering.
How many bags of concrete for steps
An 80 lb bag of pre-mixed concrete yields about 0.60 cubic feet once mixed, so it takes roughly 45 bags to make one cubic yard, 60 bags at 60 lb, or 90 bags at 40 lb. Most residential stair pours land between 0.4 and 1.5 cubic yards, which keeps them in bag territory rather than a full truck.
Bagged concrete costs more per yard than ready-mix, typically 270 to 450 dollars once you buy 45 bags, versus 125 to 195 dollars delivered by truck. For stairs alone, most homeowners still choose bags because ready-mix suppliers usually have an 8 to 10 yard minimum before short-load fees kick in. If your project also includes a slab, footing or driveway, combine the pours and run the total through the concrete calculator to see whether ordering ready-mix makes more sense.
Stringer length and rebar for concrete stairs
A precast or form-built concrete stair still needs a stringer or form reference during layout, and for a 5 step stair with a 7.5 inch rise and 10 inch run, the diagonal stringer length works out to about 50 to 63 inches depending on whether the top tread is counted or serves as the landing. A standard 8 to 10 foot 2x12 board leaves plenty of margin for the notched cuts.
Concrete stairs also need reinforcement to resist cracking under repeated foot traffic and freeze-thaw cycles. Typical practice places number 4 rebar horizontally in each step and vertically through the riser, tied into the footing below, set per the reinforcement details in ACI 332 for residential concrete.
Ready-mix cost and ordering tips for stair pours
In 2026, standard 3,000 to 4,000 PSI ready-mix concrete costs roughly 125 to 195 dollars per cubic yard delivered within about 20 miles, with many regions averaging near 140 to 165 dollars. Orders under the plant minimum, usually 8 to 10 cubic yards, add a short-load fee of 25 to 75 dollars per yard, which is why most single stair pours use bagged mix instead.
QUIKRETE Concrete Mix or QUIKRETE 5000 are both rated for building new steps, mixed on site and placed in lifts if the pour is deep. Wet the subgrade, brace the forms well since stair forms take more hydraulic pressure than a flat slab, and finish each tread with a slight forward slope so water sheds off rather than pooling.
Frequently asked questions
How long is 2x12 for a 5 step stringer?
Can you use Quikrete for stairs?
How much to pour 3 concrete steps?
How far will an 80 lb bag of concrete go?
Do concrete stairs need rebar?
References
- QUIKRETE: Concrete Steps and Ramps (project guide)
- ACI 332: Residential Concrete Code
- NRMCA: Ready Mixed Concrete
- Stairs (Wikipedia)