How Much Concrete for Stairs? Steps & Cost

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.

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 ÷ 27

Always 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 illustrative 7 inch riser and 11 inch tread dimensions after compliance is confirmed, 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.

Freshly poured concrete stair treads being smoothed with a hand trowel before a rebar-reinforced riser

Stringer length and rebar for concrete stairs

A precast or form-built stair needs geometry coordinated with the approved rise, run, landing and support details. The example dimensions are illustrative and do not select lumber or formwork.

Use the reinforcement, cover, anchorage and footing details shown in the approved design. The volume calculator does not design stair reinforcement.

Ready-mix cost and ordering tips for stair pours

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.

By Calcnaut

Formula and declared-case checks run during the build; sources are listed for readers to review. Read our method and editorial policy.

Frequently asked questions

How long is 2x12 for a 5 step stringer?

A 5 step stringer with a typical 7.5 inch rise and 10 inch run measures about 50 to 63 inches on the diagonal, so a standard 8 or 10 foot 2x12 board provides enough length for the notched cuts and the required 5 inch minimum uncut edge.

Can you use Quikrete for stairs?

Use a bagged product only if its current data sheet, mixing, placement and exposure properties satisfy the approved stair specification. Nominal compressive strength alone does not confirm suitability, and stair geometry, reinforcement, support, finish and curing still require project details.

How much to pour 3 concrete steps?

Three standard steps at 36 inches wide with a 7 inch riser and 11 inch tread need about 0.39 cubic yards of concrete, roughly 18 bags of 80 lb mix, and closer to 1.2 cubic yards if a landing is added.

How far will an 80 lb bag of concrete go?

An 80 lb bag of pre-mixed concrete yields about 0.60 cubic feet once mixed with water, so it takes roughly 45 bags to make one cubic yard, which is enough for most single stair pours without a landing.

Do concrete stairs need rebar?

Stair geometry alone does not determine reinforcement. Follow the approved details for bar size, grade, spacing, cover, anchorage and connection to supports; the concrete-volume calculator cannot design the reinforcement.

Sources and references

These references and structured source records support the method and material data used on this page.

How Much Concrete for Stairs?

Key takeaways