How many yards of concrete do I need for a wall?

Multiply length × height × thickness, all in feet, and divide by 27. A 40 ft wall 8 ft high and 8 in (0.667 ft) thick is 40 × 8 × 0.667 = 213.3 ft³, which is 7.9 yd³ before openings and waste. In metric, length × height × thickness in metres is the cubic metres straight away: 12 × 2.4 × 0.2 = 5.76 m³.

Should I subtract windows and doors from a poured wall?

Yes, when the opening is a real blockout that keeps concrete out. A 3 × 4 ft window in an 8 in wall is 3 × 4 × 0.667 = 8 ft³, about 0.3 yd³; a 0.9 × 1.2 m window in a 200 mm wall is 0.216 m³. Pipe sleeves and small penetrations are not worth taking out.

How much extra concrete should I order for a wall?

Most crews add around 5–10%: forms bulge a little, the footing top is never dead flat and the pump line holds some. The default here is 5%. Being a quarter yard over costs little; being short on a wall pour leaves a cold joint while you wait for another truck.

How many bags of concrete for a wall?

Divide the volume by what one bag makes. A typical 80 lb bag yields about 0.6 ft³, so a cubic yard is 27 ÷ 0.6 = 45 bags; a 30 kg bag makes roughly 0.014 m³, about 72 bags a cubic metre. Type the yield printed on your bag — anything beyond a yard or so is usually a ready-mix job.

Concrete wall calculator

Show the working — with your numbers

The volume of the wall you describe, less the openings, plus your waste, rounded to how concrete is sold. It does not size the wall, the footing or the steel — that comes from your drawings — and it does not allow for pilasters, a brick ledge or a stepped footing unless you add them.

Type the wall length, the pour height and the thickness between the forms, and any window or door blockouts. The tool gives the concrete in cubic yards and cubic metres, the order rounded up to the half yard (or 0.1 m³) and the bag count at the yield you enter.

Worked example

Imperial: a basement wall 40 ft long, 8 ft high and 8 in thick, with one 3 × 4 ft window blockout. Gross 40 × 8 × 0.667 = 213.3 ft³; the window is 3 × 4 × 0.667 = 8 ft³; net 205.3 ft³ = 7.6 yd³. Add 5%: 215.6 ft³ = 7.99 yd³, so you order 8 yd³ (6.1 m³). In 80 lb bags at 0.6 ft³ that would be 360 bags — a truck job.

Metric: a wall 12 m long, 2.4 m high and 200 mm thick, with one 0.9 × 1.2 m opening. Gross 12 × 2.4 × 0.2 = 5.76 m³; the opening is 0.9 × 1.2 × 0.2 = 0.216 m³; net 5.544 m³. Add 5%: 5.82 m³, so you order 5.9 m³ (about 7.6 yd³). At 0.014 m³ a 30 kg bag, 416 bags.

On the job

Walls eat more than slabs. Forms bow a hair between ties, the footing top dips, and the pump line and hopper hold concrete that never reaches the wall. On a wall pour, running short means a cold joint while you wait for the next truck — order the extra and have somewhere to put the leftover (a pad, a few post holes).

Take the openings out, leave the sleeves in. A door blockout in an 8 in wall — 3 × 6 ft 8 in — is 13.3 ft³, half a yard. A 4 in pipe sleeve is nothing. Take off what is worth a wheelbarrow.

Call the order in round numbers. Plants batch by the half yard or the tenth of a cubic metre, and many charge a short-load fee under a minimum. Watch the last truck: have the finisher call the remaining height before the plant batches the final load.

What went wrong?

Quick referencefor poured walls

Cubic yards: ft³ ÷ 27 · a cubic yard is 0.765 m³, a cubic metre is 1.308 yd³
8 in wall: 1 yd³ per 40.5 ft² of wall face (27 ÷ 0.667)
10 in wall: 1 yd³ per 32.4 ft² of wall face (27 ÷ 0.833)
200 mm wall: 1 m³ per 5 m² of wall face · 250 mm: 1 m³ per 4 m²
Bags: 0.6 ft³ (80 lb) bag: 45 a yard · 0.014 m³ (30 kg) bag: about 72 a m³

The formula

volume = (length × height − openings × width × height) × thickness × (1 + waste)

Everything in feet gives cubic feet — divide by 27 for yards. Everything in metres gives cubic metres. The order is that volume rounded up to the half yard or the tenth of a cubic metre; bags are the volume divided by your bag's yield, rounded up.

Questions

How many yards of concrete do I need for a wall?: Multiply length × height × thickness, all in feet, and divide by 27. A 40 ft wall 8 ft high and 8 in (0.667 ft) thick is 40 × 8 × 0.667 = 213.3 ft³, which is 7.9 yd³ before openings and waste. In metric, length × height × thickness in metres is the cubic metres straight away: 12 × 2.4 × 0.2 = 5.76 m³.
Should I subtract windows and doors from a poured wall?: Yes, when the opening is a real blockout that keeps concrete out. A 3 × 4 ft window in an 8 in wall is 3 × 4 × 0.667 = 8 ft³, about 0.3 yd³; a 0.9 × 1.2 m window in a 200 mm wall is 0.216 m³. Pipe sleeves and small penetrations are not worth taking out.
How much extra concrete should I order for a wall?: Most crews add around 5–10%: forms bulge a little, the footing top is never dead flat and the pump line holds some. The default here is 5%. Being a quarter yard over costs little; being short on a wall pour leaves a cold joint while you wait for another truck.
How many bags of concrete for a wall?: Divide the volume by what one bag makes. A typical 80 lb bag yields about 0.6 ft³, so a cubic yard is 27 ÷ 0.6 = 45 bags; a 30 kg bag makes roughly 0.014 m³, about 72 bags a cubic metre. Type the yield printed on your bag — anything beyond a yard or so is usually a ready-mix job.

Related tools

Spot something wrong on this page? Report it

Thanks — your report was sent.

That didn’t send. Please try again later.