Concrete Wall Calculator
To pour a 10 ft long × 4 ft tall wall at 8 in thick (the default wall thickness) you need about 0.99 cu yd of concrete plus 10% waste — roughly 49 bags of 80 lb concrete mix. Enter the wall length and height as the two dimensions, and set thickness to the wall thickness; above about 1 cu yd, ready-mix delivery is usually cheaper and faster than bags.
Reviewed by The ponderloop teamUpdated 2026-07-11How we calculate
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0 cu yd + 0% waste = 0 cu yd
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How this number is calculated
0 cu yd (no waste added) ÷ 0.0222 cu yd per bag = 0 bags
Shopping list
- 80 lb concrete mix bag
- Mixing tub
- Masonry finishing trowel
- Rebar (1/2 inch)
- Concrete wall form panels
- 4 ft level
0.0 cu yd — ~0% of a standard truck load
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Methodology & assumptions
Volume is calculated as wall length × height × (thickness in inches ÷ 12), then divided by 27 to convert cubic feet to cubic yards. A waste percentage is added for spillage and form leakage, and the result is divided by the coverage per bag (about 0.0222 cu yd for an 80 lb bag) and rounded up to the next whole bag. Most wall pours quickly exceed 1 cubic yard, at which point ready-mix delivery is usually more economical and far less labor than bags.
- ACI 318 concrete practice (waste allowance)
- Manufacturer bag-yield specs (80 lb ≈ 0.60 cu ft)
- Typical US ready-mix and bag price ranges, 2026
Worked examples
| Room | Result |
|---|---|
| 10 ft long × 4 ft tall wall, 8 in thick, standard waste | 0.99 cu yd + 10% waste ≈ 1.09 cu yd → 49 bags |
| 20 ft long × 8 ft tall foundation wall, 8 in thick, standard waste | 3.95 cu yd + 10% waste ≈ 4.35 cu yd → 196 bags (ready-mix strongly recommended) |
| 6 ft long × 3 ft tall garden wall, 6 in thick, minimal waste | 0.33 cu yd + 5% waste ≈ 0.35 cu yd → 16 bags |
Frequently asked questions
- How many bags of concrete do I need for a wall?
- Multiply the wall length by its height in feet, multiply by the wall thickness (converted from inches to feet), and divide by 27 to get cubic yards. Add 10% for waste, then divide by the coverage per bag (about 0.0222 cu yd for an 80 lb bag) and round up.
- How do I measure a wall for this calculator?
- Enter the wall LENGTH and wall HEIGHT as the two dimensions (not floor length and width), then set "Thickness" to the wall’s thickness in inches. The calculator multiplies length × height × thickness to get the total concrete volume, the same way it multiplies length × width × depth for a footing.
- Does bag size (40 lb, 60 lb, or 80 lb) change how many bags I need?
- Yes. A 40 lb bag yields about 0.011 cu yd, a 60 lb bag about 0.0167 cu yd, and an 80 lb bag about 0.0222 cu yd. This calculator assumes 80 lb bags; if you are buying 40 lb or 60 lb bags, divide the cubic yardage by that bag’s yield instead to get an accurate bag count.
- Should I use ready-mix for a wall pour?
- Almost always for anything beyond a small garden wall. A single 8 ft tall, 20 ft long, 8 in thick foundation wall section is already around 4 cu yd — roughly 200 bags of mix — which is impractical to hand-mix. Once you are above about 1 cu yd, a ready-mix truck or mini-mix delivery is faster and usually cheaper per yard.
- Do I need rebar or forms for a concrete wall?
- Yes — poured concrete walls are almost always reinforced with rebar and require formwork on both faces to hold the wet concrete in shape while it cures. This calculator estimates concrete volume only; rebar sizing and form design should follow your local code or an engineer’s plan.