How do I calculate concrete for a wall?

Multiply length by height to get the elevation area, subtract any openings, then multiply by the wall thickness. Add the footing separately as its own length by width by depth. Finally add a wastage allowance, which for walls should be at least ten percent. The two steps most often skipped are the footing, which can be a quarter of the total, and deducting openings at full thickness rather than treating them as an area reduction.

Do I subtract door and window openings?

Yes, and at the full wall thickness. This trips people up because it feels like an area calculation: a 1.89 m² door in a 200 mm wall removes 0.378 m³ of concrete. Deducting only the face area and then multiplying the remainder by thickness gives the right answer, but subtracting the opening after multiplying by thickness — which is the more natural order for many people — quietly gives the wrong one. The calculator handles the order for you.

Should I include the footing in the same pour?

Usually not in the same pour, but definitely in the same order if they are going in on the same day. The footing is normally poured first and allowed to set so the wall forms have something solid to stand on and be fixed to. Where they are poured separately, the joint between them is a planned construction joint with reinforcement carried through it, which is quite different from an accidental cold joint. What matters for ordering is that you count both volumes, since the footing is easy to overlook and rarely small.

How thick should a concrete wall be?

It depends entirely on what the wall is doing. A free-standing garden or screen wall might be 150 mm. A foundation or stem wall carrying a building above is commonly 200 mm. Basement walls are typically 250 mm or more, and retaining walls start around 300 mm and go up sharply with retained height. Anything holding back earth much above a metre should be designed rather than picked from a table, because the pressure grows with the square of the height and the failure mode is the whole wall rotating out at the base.

Why does the calculator show formwork area?

Because on a cast wall it is frequently the bigger cost. Concrete has a price per cubic metre that is easy to look up, while formwork is priced by the square metre of contact face and includes the ties, the bracing, the labour to build it and the labour to strike it afterwards. A wall has two faces and two ends, so the formwork area is a little over twice the elevation, and pricing a wall on concrete alone can understate the job substantially. Openings add more, since each one needs a box-out around its perimeter.

What happens if I cannot pour the whole wall at once?

You get a cold joint, which is a plane where fresh concrete met concrete that had already begun to set and did not bond to it. It is both structurally weaker than the surrounding material and a preferential path for water, which matters enormously for a basement or retaining wall. If a break is unavoidable, it should be planned as a proper construction joint — stopped at a sensible location, with reinforcement carried through and the surface prepared and cleaned before the next pour — rather than simply happening because the concrete ran out.

How do I pour a wall in lifts?

In layers of around 400 to 500 mm, vibrating each one into the layer below so the two combine into a single mass. The vibrator should penetrate a little way into the previous lift, which is what knits them together. Placing a full-height wall in one drop is worse rather than better: concrete falling more than a metre or so segregates, with the coarse aggregate separating from the paste, and you end up with stone at the bottom and weak laitance at the top.

How much does a concrete wall weigh?

Around 2,400 kilograms per cubic metre for normal-weight reinforced concrete, so a 12 metre wall at 2.4 metres high and 200 mm thick comes to roughly 13 tonnes before the footing. It is worth knowing because it drives whether the ground beneath needs a wider footing to spread the load, and because it is the reason formwork has to be braced properly — the horizontal pressure of wet concrete against the forms is substantial, and it is greatest at the bottom where it is hardest to fix a bulge afterwards.

How much waste should I allow on a wall pour?

Ten percent as a floor, and more if the formwork is improvised. Walls lose material in ways slabs do not: forms leak at every joint, they bow slightly under pressure so the finished wall is fractionally thicker than drawn, and the last of each load sticks in the chute and the pump line. The asymmetry also matters more here. Surplus concrete on a slab is an inconvenience; running short halfway up a wall means a cold joint at whatever height the concrete stopped, which is permanent.

Concrete Wall Volume Calculator

Working out the concrete for a wall is length times height times thickness, and that answer is right until you notice the two things it leaves out. The first is that almost every cast wall sits on a strip footing, poured as part of the same job and often accounting for a quarter or more of the total...

THE WALL

WALLS

LENGTH (m)

HEIGHT (m)

WALL THICKNESS (mm)

OPENINGS PER WALL

DOORS

WIDTH (m)

HEIGHT (m)

WINDOWS

WIDTH (m)

HEIGHT (m)

Include a strip footing

FOOTING WIDTH (mm)

FOOTING DEPTH (mm)

CONCRETE REQUIRED

8.30 m³

including 10% waste · 19.91 tonnes · 10.85 yd³

WALL

5.38 m³

FOOTING

2.16 m³

FORMWORK

54.8 m²

This is a ready-mix job. At 8.30 m³ you would be mixing 489 bags by hand. More importantly, a wall wants to be poured continuously — a break long enough for the lower concrete to start setting leaves a cold joint running through the wall, which is both a weak plane and a path for water. 2 loads of ready-mix does it in one go.

Gross elevation

28.80 m²

Openings

1.89 m²

Wall volume

5.382 m³

Openings deducted

0.378 m³

Footing volume

2.160 m³

Total before waste

7.542 m³

Weight

19.91 t / 43,896 lb

Formwork area

54.78 m²

Bags of premix

489

Ready-mix loads

POURING IT

Pour the footing first — 2.160 m³ — and let it set before standing the wall forms on it.

Build and brace the forms for 54.8 m² of face. Wet concrete pushes outward hard, and a form that bows shows in the finished wall permanently.

Place 5.382 m³ in the wall in lifts of about 500 mm, vibrating each lift into the one below so they knit together.

Pour continuously. A break long enough for the lower concrete to stiffen leaves a cold joint through the wall — a weak plane and a water path both.

THE WALL

Openings come out through the full thickness. The 1.89 m² of doors and windows removes 0.378 m³ of concrete, not just an area — a hole in a wall goes all the way through. What is left is 5.382 m³ in the wall, plus 2.160 m³ in the footing beneath it.

Formwork comes to 54.8 m² across both faces and the two ends, plus roughly 1.20 m² of box-outs around the openings. That is the figure to price shuttering against, and on a wall it often costs more than the concrete does.

Live calculation · updates as you type

Created with❤️byeaglecalculator.com

HOW TO USE

1
Enter how many identical walls you are pouring, then the length, height and thickness of one of them. The thickness selector is separate because walls are quoted in metres or feet but their thickness in millimetres or inches.
2
Add doors and windows per wall. These are deducted through the full thickness, since an opening goes all the way through — deducting only the face area would leave the volume unchanged, which is the common mistake.
3
Leave the footing ticked if the wall sits on a strip footing and set its width and depth. Untick it if the footing is a separate pour you have already accounted for, or if there is not one.
4
Read the volume, the weight, and the two supply routes. The formwork figure beside them is what to price shuttering against — on a wall it is often the larger cost of the two.

THE FORMULAS

Gross elevationlength × height × walls

Net elevationgross − openings

Wall volumenet elevation × thickness

Openings removedopening area × thickness

Footing volumelength × width × depth × walls

Total(wall + footing) × (1 + waste)

Weightvolume × 2400 kg/m³

Formwork2 × net elevation + 2 × thickness × height

WALL THICKNESS GUIDE

Thickness	Typical use	m³ per m² of wall	yd³ per 100 ft²
150 mm / 5.9 in	Light garden and screen walls	0.150	1.82
200 mm / 7.9 in	Foundation and stem walls	0.200	2.43
250 mm / 9.8 in	Basement walls, moderate retained height	0.250	3.04
300 mm / 11.8 in	Retaining walls, deeper basements	0.300	3.65
400 mm / 15.7 in	Heavily loaded or deep retaining walls	0.400	4.86

Thickness is a structural decision that depends on retained height, soil, surcharge loads and local code — this table shows where each thickness is commonly found, not what your wall needs. Anything retaining earth above about a metre should be designed rather than assumed.

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Last updated: July 28, 2026 · Formula verified · Eagle-eyed accuracy for every calculation.