Concrete wall calculator
A wall 20 ft long, 4 ft high and 8 in thick holds 1.98 cubic yards of concrete. Order 2.17 yards with 10% extra.
How it works
A straight wall is a box: length × height × thickness. For a foundation with several walls, either add the wall lengths together (measuring along the center of the wall so the corners are counted once) or enter each wall size with the number of walls that share it. Leave out door and window openings by working out their volume separately and subtracting it.
20 ft × 4 ft × 8 in = 53.33 cu ft
53.33 cu ft ÷ 27 = 1.98 cu yd
With 10% extra: 2.17 cu yd
The footing under the wall is a separate pour with its own volume; the footing calculator handles it.
Cubic yards per 10 ft of wall
| Wall height | 6 in thick | 8 in thick | 10 in thick | 12 in thick |
|---|---|---|---|---|
| 2 ft | 0.37 | 0.49 | 0.62 | 0.74 |
| 3 ft | 0.56 | 0.74 | 0.93 | 1.11 |
| 4 ft | 0.74 | 0.99 | 1.23 | 1.48 |
| 6 ft | 1.11 | 1.48 | 1.85 | 2.22 |
| 8 ft | 1.48 | 1.98 | 2.47 | 2.96 |
Wall forms bow outward under the weight of wet concrete, which is one of the reasons the ready-mix industry advises ordering at least 4 to 10 percent more than the measured volume. A wall more than a couple of yards is almost always a ready-mix pour; a low garden wall can be mixed from bags, at 45 bags of 80 lb mix per cubic yard.
Sources
- CIP 8: Discrepancies in Yield (Concrete in Practice series), National Ready Mixed Concrete Association, 2016 edition. Order at least 4 to 10 percent more than the measured volume; 1/8 in extra on a 4 in slab is a 3 percent shortfall.
- QUIKRETE Concrete Mix (No. 1101) data sheet, The QUIKRETE Companies, revised October 2022. Bag yields: 40 lb 0.30 cu ft, 50 lb 0.375, 60 lb 0.45, 80 lb 0.60, 90 lb 0.675; about 140 lb per cubic foot.