How much concrete is in an 8-inch foundation wall?

An 8 in wall holds 0.667 ft³ per square foot of wall face — almost exactly 1 yd³ per 40 ft² of wall. A typical 8 ft tall, 40 ft long wall face (320 ft²) therefore needs about 8 yd³ before waste.

Should I subtract window and door openings?

Yes, when they're large. A single basement window buck (say 32 × 16 in ≈ 3.5 ft²) is noise inside the waste allowance, but a walkout door plus three windows in one wall can exceed 60 ft² — nearly 1.5 yd³ in an 8 in wall. The calculator's openings field handles this.

How fast can I fill a wall form?

Form pressure is governed by pour rate and concrete temperature (ACI 347). Standard residential panel forms are commonly rated around 600–800 psf, which at 70°F works out to roughly 4–5 ft of placement per hour. Filling a full-height 8 ft wall in one fast pass can blow out forms — pour in lifts around the wall instead.

What slump should wall concrete be?

5–6 in slump places well in walls; anything stiffer honeycombs around rebar and anything wetter is usually water added on site, which cuts strength (each added gallon per yard costs roughly 200 psi). Order a mid-range water-reducer mix rather than adding water at the truck.

Is an ICF wall calculated the same way?

The concrete core is — length × height × core thickness (typically 6 or 8 in) minus openings. The foam form adds no concrete. ICF suppliers publish per-form volumes; they agree with this calculator to within a percent or two.

Concrete · Walls

Concrete Wall Calculator

Length × height × thickness, minus openings, plus the right waste factor. The notes below cover the part calculators can't do: getting the concrete into the form safely.

1 yd³
per 40 ft² of 8 in wall: 4–5 ft/hr
safe pour rate @ 70°F: 5–6 in
target slump for walls: 2 sides
of formwork required

Concrete Wall Calculator

Cast-in-place walls: foundations, retaining walls, stem walls. Subtracts window and door openings.

Quick answer

How much concrete do I need for a foundation wall?

A 20 ft run of 8-inch foundation wall, 8 ft high, needs about 4.35 yd³ of concrete with a 10% waste allowance — roughly 8 tonnes. Openings like windows and doors subtract directly from this volume before the waste factor is applied.

Rule of thumb:: An 8-inch wall uses about 1 cubic yard per 40 ft² of wall face, before waste.
Formula:: Order (yd³) = ((Run × Height − Openings) × Thickness ÷ 27) × (1 + waste)

Walls by common run length

8 in thick, 8 ft high, no openings, 10% waste included. Cost uses the $150–180/yd³ delivered ready-mix range from our concrete cost guide.
Wall run (8 in × 8 ft high)	Order (yd³)	Approx. weight	Est. material cost
20 ft	4.35 yd³	8.0 t	$653–783
40 ft	8.69 yd³	16.0 t	$1,304–1,564
60 ft	13.04 yd³	23.9 t	$1,956–2,347
80 ft	17.38 yd³	31.9 t	$2,607–3,128
100 ft	21.73 yd³	39.9 t	$3,260–3,911

Wall volume math, with openings

Formula

V = (L × H − A₀) × t × (1 + waste)

L: wall length (ft or m)
H: wall height (ft or m)
A₀: total area of openings (ft² or m²)
t: wall thickness (ft or m)

Corners are counted once: measure lengths along the wall centerline, or measure outside faces and accept ~1% overage on a rectangular foundation.

For a full foundation, run each wall face through the calculator (or sum the centerline perimeter and treat it as one long wall). Remember the footing below is a separate volume — the footing calculator handles that, and the two pours are usually days apart anyway.

Worked example: basement with a walkout

Worked example

A 36 × 28 ft basement, 8 ft walls, 8 in thick. One walkout door (7 × 4 ft) and four window bucks (each 32 × 16 in).

1
Centerline perimeter
2 × (36 + 28) = 128 ft
2
Gross wall face
128 × 8 = 1,024 ft²
3
Openings
28 ft² (door) + 4 × 3.6 ft² = 42.2 ft²
4
Net face × thickness
(1,024 − 42.2) × 0.667 = 654.8 ft³
5
Add 10%, convert to yards
654.8 × 1.10 ÷ 27 = 26.7 yd³

Result: Order 27 yd³ — that's three 9-yard trucks, so sequence them 45 minutes apart.

Formwork pressure: the safety constraint

Concrete per square foot of wall

Yards per 100 ft² of wall face — memorize your thickness and you can estimate standing in the excavation.

Concrete per 100 ft² of wall face

6 in wall1.85yd³

8 in wall2.47yd³

10 in wall3.09yd³

12 in wall3.7yd³

Wall pour questions

How much concrete is in an 8-inch foundation wall?: An 8 in wall holds 0.667 ft³ per square foot of wall face — almost exactly 1 yd³ per 40 ft² of wall. A typical 8 ft tall, 40 ft long wall face (320 ft²) therefore needs about 8 yd³ before waste.
Should I subtract window and door openings?: Yes, when they're large. A single basement window buck (say 32 × 16 in ≈ 3.5 ft²) is noise inside the waste allowance, but a walkout door plus three windows in one wall can exceed 60 ft² — nearly 1.5 yd³ in an 8 in wall. The calculator's openings field handles this.
How fast can I fill a wall form?: Form pressure is governed by pour rate and concrete temperature (ACI 347). Standard residential panel forms are commonly rated around 600–800 psf, which at 70°F works out to roughly 4–5 ft of placement per hour. Filling a full-height 8 ft wall in one fast pass can blow out forms — pour in lifts around the wall instead.
What slump should wall concrete be?: 5–6 in slump places well in walls; anything stiffer honeycombs around rebar and anything wetter is usually water added on site, which cuts strength (each added gallon per yard costs roughly 200 psi). Order a mid-range water-reducer mix rather than adding water at the truck.
Is an ICF wall calculated the same way?: The concrete core is — length × height × core thickness (typically 6 or 8 in) minus openings. The foam form adds no concrete. ICF suppliers publish per-form volumes; they agree with this calculator to within a percent or two.

Compare your wall estimate against ready-mix pricing in the cost guide

Related calculators & guides

Concrete Footing CalculatorStrip footings by total run, width and depth.Calculator Concrete Column CalculatorRound sonotubes and square piers, any count.Calculator Concrete Curing GuideStrength gain timeline and curing methods that work.Guide

Sources & references

[1]ACI 347R-14: Guide to Formwork for Concrete — American Concrete Institute, 2014
[2]ASTM C94/C94M: Standard Specification for Ready-Mixed Concrete — ASTM International, 2024
[3]ACI 318-19: Building Code Requirements for Structural Concrete — American Concrete Institute, 2019