Concrete, rebar and formwork for a poured wall — single walls or a full perimeter measured on the centreline.
Concrete Wall Calculator
Inputs
Windows, doors and beam pockets. A basement window is about 8 ft².
From your plan or IRC Table R404.1.2 — it depends on backfill height and soil.
Formed walls waste less than trenches — the form is the dimension.
Results
Concrete to order
8.30 yd³
V = (length × height − openings) × thickness ÷ 27
Calculated with BuildCalculators.com
Calculated with BuildCalculators.com · buildcalculators.com/concrete-wall-calculator
Estimates are for planning only — confirm quantities with your supplier or contractor before ordering.
A poured wall is the easiest volume on this site — length by height by thickness — and the hardest thing to actually order, because the concrete is only one of four quantities that come off the same wall and they all scale differently. Double the thickness and the concrete doubles while the formwork does not move. Deduct a window and the concrete drops while the formwork goes up.
So this calculator gives you all four: the concrete, the vertical steel, the horizontal steel, and the form face area that the forming will actually be priced against. The perimeter mode works the run out from building dimensions on the centreline, which is what stops the four corners being counted twice.
V = (run × height − openings) × thickness ÷ 272(L − t) + 2(W − t)floor(run × 12 ÷ spacing) + 1floor(height × 12 ÷ spacing) + 1net wall face × 2Take a 40 by 24 ft building with 8 inch walls. Using the outside dimensions gives a 128 ft perimeter; the real centreline run is 2(40 − 0.67) + 2(24 − 0.67), or 125.3 ft. The 2.7 ft difference is the four corners, where two walls overlap and the concrete is only there once. On an 8 ft high wall that is a third of a cubic yard you would otherwise order and pay for twice.
Spacing measures the distance between bars, so the number of bars is always one more than the number of gaps. A 40 ft wall with vertical bars at 48 inches has ten gaps and eleven bars. This is the same arithmetic that catches people on slab grids, and it is off by one in the direction that leaves you short.
The spacings you enter here get counted, not checked. What your wall actually needs comes from IRC Table R404.1.2 or from an engineer, and it depends on the wall height, its thickness, the soil class and — most of all — how much unbalanced backfill pushes against it. A basement wall retaining 7 ft of soil is a different structure from a 4 ft garden wall of the same thickness, and no rule of thumb bridges that gap safely.
Three inches of concrete where it is cast directly against earth, an inch and a half on formed faces that will be exposed to earth. Bars pushed tight against a form have no protection: water reaches them, they rust, rust occupies more volume than steel, and the face of the wall spalls off in sheets a decade later. Chairs and spacers are cheap.
A window buck removes its own area of concrete and then adds two faces of formwork, bracing to stop it floating up in the pour, and a lintel or bond beam over the top. The form area in the results covers the wall faces only. On a wall with several openings, the forming labour can rise while the concrete bill falls — which is exactly backwards from how most people budget it.
Formed walls go in in lifts and get vibrated as they rise. That is not a bagged job at any realistic size: a 40 ft wall 8 ft high in 8 inch thickness is nearly 8 cubic yards, or 356 bags. Placing it in batches over a day leaves a cold joint running horizontally through the wall at whatever height you stopped — a plane of weakness, and on a basement wall, a place for water to come through.
No openings, bars at 48 in vertical and 24 in horizontal.
8.30 yd³ with waste, 288 lin ft of rebar
Also 640 ft² of form face, both sides. That number, not the concrete, is what a forming subcontractor prices from.
8 ft high, 8 in thick, 32 ft² of openings deducted.
25.17 yd³ with waste
Using the 128 ft outside perimeter instead would have added 0.53 yd³ — about $90 of concrete bought to fill corners that are already full.
Low freestanding wall, bars at 32 in vertical.
2.33 yd³ with waste
Still a truck, and still worth one — 2.33 yards is 105 bags. A freestanding wall this low usually needs far less steel than a retaining one, but it needs a footing just the same.
| Thickness | Volume | Cubic yards | 80 lb bags |
|---|---|---|---|
| 6 in | 50.0 ft³ | 1.85 yd³ | 84 |
| 8 in | 66.7 ft³ | 2.47 yd³ | 112 |
| 10 in | 83.3 ft³ | 3.09 yd³ | 139 |
| 12 in | 100.0 ft³ | 3.70 yd³ | 167 |
ACI 318 minimums for cast-in-place concrete.
| Condition | Minimum cover |
|---|---|
| Cast against and permanently exposed to earth | 3 in |
| Formed, then exposed to earth or weather (#6 and larger) | 2 in |
| Formed, then exposed to earth or weather (#5 and smaller) | 1½ in |
| Not exposed to weather or earth | ¾ in |
Poured foundation walls run $25–$60 per square foot of wall face installed in 2026, taking in forming, steel, concrete, placement and stripping. The concrete itself is $140–$200 per cubic yard, which on a typical 8 inch wall is only about $4 per square foot of face — well under a fifth of the installed price.
Forms have to be set plumb, tied against several tons of lateral pressure, and stripped clean. Renting forms runs $1.50–$4 per square foot of face per use; buying and building them costs more up front and pays off only across several jobs. This is why the form face area is a headline result here rather than a footnote.
Going from 8 to 10 inches adds 25% to the concrete and almost nothing to the forming, since the forms are the same panels set further apart. Going from 8 to 10 feet high adds 25% to both, plus taller bracing and a slower pour. Where a wall needs more capacity, thickness is usually the cheaper way to buy it — but that is a structural decision, not a budget one.
A truck that can chute straight into the forms is the cheap case. Anything else means a pump at $800–$1,500 for the day regardless of volume, and on a tight or sloping site that is effectively a fixed cost of pouring at all. Worth establishing before the forms go up, not after.
The four corners get counted twice. Run the perimeter on the centreline — outside dimensions less one wall thickness per side — or you buy concrete to fill corners that are already full.
A 40 ft wall at 48 inch spacing has ten gaps and eleven bars. Dropping the plus-one leaves you one bar short in every direction, and it is always the end bar that goes missing.
This tool counts what you tell it. Wall reinforcement depends on height, thickness, soil class and unbalanced backfill, and comes from IRC Table R404.1.2 or an engineer. A garden wall and a basement wall of the same size are not the same structure.
Steel needs 3 inches against earth and 1½ inches on formed faces exposed to earth. Bars tied against the form rust, and rusting steel spalls the face off the wall.
A window removes concrete and adds formwork, bracing and a lintel. On a wall with several openings the labour goes up while the concrete goes down.
A wall is placed in continuous lifts and vibrated. Stopping for hours leaves a cold joint across the whole wall — a weakness, and on a basement wall a route for water.
Length × height × thickness, divided by 27, minus any openings. A 40 by 8 ft wall at 8 inches thick is 213 cubic feet, or 7.9 cubic yards. Per 100 square feet of wall face, an 8 inch wall takes 2.47 cubic yards.
Run the perimeter on the CENTRELINE, not the outside face — outside dimensions less one wall thickness per side. A 40 by 24 ft building with 8 inch walls has a 125.33 ft centreline, not 128 ft. The 2.67 ft difference is the four corners, where two walls overlap and the concrete is only there once.
That depends on the wall height, thickness, soil class and how much unbalanced backfill pushes against it, and it comes from IRC Table R404.1.2 or an engineer. This calculator counts the steel for a spacing you supply — a 40 ft wall with vertical bars at 48 inches takes 11 bars, because spacing counts the gaps and there is always one more bar than gaps.
Three inches where concrete is cast directly against earth, and 1½ inches on formed faces later exposed to earth or weather for #5 bars and smaller. Bars tied against the form rust, and rusting steel expands and spalls the face off the wall.
$25–$60 per square foot of wall face installed in 2026, covering forming, steel, concrete, placement and stripping. The concrete alone is about $4 per square foot on an 8 inch wall — under a fifth of the total, because forming is most of the work.
Not in horizontal sections. A wall goes in in continuous lifts and gets vibrated as it rises; stopping for hours leaves a cold joint running through the whole wall — a plane of weakness, and on a basement wall a route for water. Vertical construction joints at planned locations are a different thing and are fine.
For a foundation, poured is usually faster and monolithic, and often cheaper once forming is priced in. Block wins where access is tight — no truck or pump, material carried in by hand — and where the work has to happen in stages by one person.
Slabs, footings and columns in cubic yards and bags
Volume, rebar and code minimum size
Blocks, mortar bags and core fill
Grid bar counts, length and weight by size
Step volume and riser layout
Installed cost by finish, material shown separately
Embed the Concrete Wall Calculator anywhere — it is free, stays in sync with this page, and sizes itself to fit. The only condition is the credit line in the snippet, which links your readers to the full version with the formulas and worked examples.
This calculator uses published constants from named industry sources, each asserted in an automated test that runs on every build. The formula is printed with the result above, and any correction we make is logged on the changelog.
It is a planning estimate. It does not replace an engineer, a site visit or a written quote — confirm quantities with your supplier before ordering.