★ CONSTRUCTION · CONCRETE · STAIRS
Four 48 in wide steps need 26.28 ft³ (0.97 yd³) of concrete: 59 × 60-lb bags, or a ready-mix truck at $145.99. Ready-mix is cheaper by $119.51 at this size — bags only win on the smallest jobs. Enter any staircase, in inches or metric, and get the volume, the bag count with waste, and the honest price comparison.
Four steps, 7 in riser, 11 in tread, 48 in wide, on a 4 in base: 21.39 ft³ of steps plus 4.89 ft³ of base, 26.28 ft³ total (0.97 yd³). That is 59 × 60-lb bags or 44 × 80-lb bags, or ready-mix at $145.99. The calculator below sizes your staircase at any dimensions, in inches or metric.
A staircase is a stack of triangular prisms. The bottom step is one riser tall, the next is two, the next three, and so on — so the volume of the steps is width × riser × tread × (1 + 2 + … + n), and 1 + 2 + … + n is n(n+1)/2. For 4 steps that is 4 × 5 / 2 = 10 riser-heights of concrete: 48 × 7 × 11 × 10 = 36,960 cubic inches, divided by 1,728 to get 21.39 ft³. The base is a simple slab: width × (n × tread) × base thickness, 48 × 44 × 4 = 8,448 cubic inches, or 4.89 ft³. Total 26.28 ft³, which is 0.97 yd³ (divide by 27). A 60-lb bag yields 0.45 ft³ and an 80-lb bag 0.60 ft³, so the bag counts are the total divided by the yield, rounded up: 59 and 44. With 10% waste the total becomes 28.91 ft³, or 65 × 60-lb bags.
Setup: 4 steps; riser 7 in; tread 11 in; width 48 in; base 4 in.
Line 1 — steps volume. 48 × 7 × 11 × 4 × 5 / 2 = 36,960 in³ / 1,728 = 21.39 ft³.
Line 2 — base volume. 48 × (4 × 11) × 4 = 8,448 in³ / 1,728 = 4.89 ft³.
Line 3 — total volume. 21.39 + 4.89 = 26.28 ft³ = 26.28 / 27 = 0.97 yd³.
Line 4 — 60-lb bags. ceil(26.28 / 0.45) = 59 bags (48 for the steps alone, without the base).
Line 5 — 80-lb bags. ceil(26.28 / 0.60) = 44 bags (36 steps-only).
Line 6 — with 10% waste. 26.28 × 1.10 = 28.91 ft³ → 65 × 60-lb bags (49 × 80-lb).
Line 7 — ready-mix vs bags. Ready-mix: 0.97 yd³ × $150/yd³ = $145.99. Bags: 59 × $4.50 = $265.50. Ready-mix is cheaper by $119.51.
3 steps: total 16.50 ft³ (0.61 yd³), 37 × 60-lb bags. A small stoop is the one size where bags can compete — and even here ready-mix at $91.67 beats $166.50 of bags.
6 steps: total 52.25 ft³ (1.94 yd³), 117 × 60-lb bags, ready-mix $290.28 against $526.50 of bags. Six steps is nearly two cubic yards — mixing 117 bags by hand is a full day of hard labour, and the truck is $236.22 cheaper.
Wide steps, 72 in: the same 4 steps need 39.42 ft³ (1.46 yd³). Volume scales with width, so a grand 6 ft staircase takes half again as much concrete.
Metric: 4 steps, riser 180 mm, tread 280 mm, width 1200 mm, base 100 mm — total 0.74 m³ (0.7392), or 26.10 ft³. The metric staircase is almost the same size as the imperial default, just a touch smaller.
Reverse — bags on hand: 20 × 80-lb bags hold 12.00 ft³, which pours 2 full steps (6.42 ft³, 11 bags). Three steps need 12.83 ft³, or 22 bags — so 20 bags leave you one step short.
The calculator assumes a solid staircase poured against a house or retaining wall, with a rectangular base slab under the full run of steps. It does not subtract for a hollow core, a sloped underside, or rebar — rebar displaces almost nothing, and a hollow form needs its own calculation. Bag yields are standard manufacturer figures: a 60-lb bag yields 0.45 ft³ and an 80-lb bag 0.60 ft³ of mixed concrete. Prices are illustrative: ready-mix at $150 per cubic yard, 60-lb bags at $4.50, 80-lb bags at $6.00 — real prices vary by region and by delivery fees, and most ready-mix suppliers charge a short-load fee under one cubic yard, which can erase the saving on the smallest jobs. The 10% waste figure is for spillage, over-excavation, and form leakage. Rounding convention: all math runs on unrounded values and rounds only for display; bag counts always round up, because a half bag does not exist at the store.
| Output | Formula | What it means |
|---|---|---|
| Steps volume | width × riser × tread × n(n+1)/2 / 1,728 | 21.39 ft³ of stepped concrete. |
| Base volume | width × (n × tread) × base / 1,728 | 4.89 ft³ under the steps. |
| Total volume | steps + base | 26.28 ft³ = 0.97 yd³. |
| 60-lb bags | ceil(total / 0.45) | 59 bags (48 steps-only). |
| 80-lb bags | ceil(total / 0.60) | 44 bags (36 steps-only). |
| With 10% waste | ceil(total × 1.10 / bag yield) | 65 × 60-lb (49 × 80-lb). |
| Ready-mix cost | yd³ × $150 | $145.99 delivered. |
| 60-lb bag cost | bags × $4.50 | $265.50 at the store. |
The math is exact for the numbers you enter: steps volume is width × riser × tread × n(n+1)/2 divided by 1,728, base volume is width × run × base thickness divided by 1,728, cubic yards are cubic feet divided by 27, and bag counts are the volume divided by the bag yield, rounded up. But the inputs carry the assumptions. The staircase is assumed solid: a hollow core, a sloped soffit, or a staircase poured in two lifts needs its own volume calculation, and the base is assumed to run the full length of the steps. Bag yields (0.45 ft³ for 60-lb, 0.60 ft³ for 80-lb) are standard manufacturer figures; real yields vary slightly with mix and water. Prices are illustrative — ready-mix $150/yd³, 60-lb bags $4.50, 80-lb bags $6.00 — and real prices vary by region, delivery fees, and short-load charges under one cubic yard, which can erase the truck's advantage on the smallest jobs. Code notes, from the International Residential Code: the maximum riser is 7.75 in and the minimum tread is 10 in, and the comfort rule is 2 × riser + tread = 24–26 in — the default (2 × 7 + 11 = 25) sits in the middle. Check your local code before you build: some jurisdictions tighten these numbers, and all of them require a handrail above a certain height. Measure the real rise from the finished grade to the finished porch, not from the dirt, or the top step will be the wrong height.
Bright Side Kit. "Concrete Steps Calculator: Volume, Bags & Cost Compared" https://brightoolbox.com/concrete-steps-calculator/ Accessed October 24, 2026.26.28 ft³ (0.97 yd³). Four steps at 7 in riser, 11 in tread, 48 in wide need 21.39 ft³ of steps plus 4.89 ft³ of base. That is 59 x 60-lb bags or 44 x 80-lb bags — or a ready-mix truck at $145.99.
59 x 60-lb bags for the default 4-step staircase. Divide the total volume by the bag yield (0.45 ft³ for a 60-lb bag, 0.60 ft³ for an 80-lb bag) and round up. With 10% waste, order 65 x 60-lb bags. Three steps take 37 bags; six steps take 117.
Ready-mix, at this size. Ready-mix costs $145.99 for 0.97 yd³ against $265.50 of 60-lb bags — cheaper by $119.51. Bags only win on the very smallest stoops, and even a 3-step run is cheaper by truck once the short-load fee is counted.
Steps volume = width x riser x tread x n(n+1)/2. The steps form a staircase of triangular prisms: the bottom step is one riser tall, the next two, and so on, so the sum is n(n+1)/2 riser-heights. Add the base (width x run x thickness) and divide by 1,728 for cubic feet.
Code allows a riser up to 7.75 in and a tread of at least 10 in. The comfortable rule is 2 x riser + tread = 24–26 in. The default here (2 x 7 + 11 = 25) sits in the middle. Check your local code — some jurisdictions tighten these numbers.
0.45 ft³. An 80-lb bag yields 0.60 ft³. Those are standard manufacturer figures. Always round bag counts up — a half bag does not exist at the store, and running short mid-pour is the worst way to save money.
Yes. Switch the units to millimetres and enter the riser, tread, width, and base in mm. A 1200 mm wide staircase with 180 mm risers and 280 mm treads needs 0.74 m³ (0.7392), or 26.10 ft³.
Two full steps. Twenty 80-lb bags hold 12.00 ft³, and two steps at the default size need 6.42 ft³ (11 bags). Three steps need 12.83 ft³, or 22 bags — so 20 bags leave you one step short.