Concrete Wall Calculator
A wall 20 ft long, 4 ft high, and 8 in thick is 53.33 cubic feet, 1.98 cubic yards, 1.51 cubic meters, and 89 bags when the yield box stays at 0.60.
Last updated . Length, height, and thickness start at 20 ft, 4 ft, and 8 in. The trapezoid widths stay hidden until that profile is chosen.
A concrete wall calculator for a straight wall, a rectangular curb, or a curb whose face is wider at the bottom. Volume is the section times the run. Bag count uses the yield you type.
Box-shaped pours, slabs, and the 0.5 ft³ order line live on the concrete calculator. Premix yields for several bag weights live on the concrete bag calculator. A footing prism is the footing calculator.
Wall or curb
Example starts: a 20 ft by 4 ft wall, 8 in thick. The trapezoid fields start at a 6 in top and a 12 in bottom, and they are used only for that profile. Yield opens at 0.60. Density opens at 2400. A blank extra percent is treated as zero.
Results
How the wall and curb volumes are calculated
Every entry is converted to feet first. A rectangle multiplies length, height, and thickness. A trapezoid curb multiplies length and height by the average of the two widths, which is the area of a trapezoid times the run. The opening wall is 20 × 4 × (8 ÷ 12) = 160 ÷ 3 = 53.333… cubic feet. Dividing by 27 gives 1.975308… cubic yards, shown as 1.98. Cubic meters multiply the unrounded cubic feet by 0.3048³, which is 1.51023… and shows as 1.51.
Kilograms multiply those cubic meters by the density box. Short tons divide the kilograms by 907.18474. At 2400 the opening wall is 3,624.56 kg and 3.995 short tons, and the ton line rounds to 4.00. The 2400 figure is the planning weight already used for pours on the concrete page. Replace it if the mix you are placing has a different unit weight. This page does not design the wall, pick reinforcement, or check a code thickness.
The bag line takes that ordered volume, divides by the yield sitting in the box, and rounds up to a whole bag. The yield box opens at 0.60 so the count matches the 80 lb starting point printed on the concrete page. 53.333… ÷ 0.60 = 88.888…, which rounds up to 89. An exact multiple would stay on that whole number. An extra percent grows the volume before the bag division. Ten percent on the opening wall is 58.666… cubic feet, 2.17 cubic yards, and 98 bags.
The trapezoid example keeps the 20 ft run, sets the height to 6 in, and uses a 6 in top with a 12 in bottom. The mean width is 9 in, or 0.75 ft, and 20 × 0.5 × 0.75 = 7.5 cubic feet. That is 0.277… cubic yards, shown as 0.28, and 13 bags at 0.60. Switching only the profile name, from wall to rectangular curb, does not change the arithmetic.
Worked volumes
| Case | ft³ | yd³ | m³ | Short tons | Bags |
|---|---|---|---|---|---|
| 20 ft × 4 ft × 8 in, no extra | 53.33 | 1.98 | 1.51 | 4.00 | 89 |
| Same wall, extra percent 10 | 58.67 | 2.17 | 1.66 | 4.39 | 98 |
| 20 ft curb, 6 in high, 6 in top, 12 in bottom | 7.50 | 0.28 | 0.21 | 0.56 | 13 |
| 6 m × 1.2 m × 200 mm | 50.85 | 1.88 | 1.44 | 3.81 | 85 |
The 6 m wall is 6 × 1.2 × 0.2 = 1.44 cubic meters before any display rounding, which is why the meter line reads 1.44 and the kilogram line reads 3,456.00 at 2400. Footings, round piers, and stair blocks stay on their own pages. A price is not estimated here.
Concrete wall questions
How much concrete is a 20 ft by 4 ft wall that is 8 in thick?
Leave Profile on Wall, rectangle. Leave length at 20 ft, height at 4 ft, thickness at 8 in, extra percent at 0, bag yield at 0.60, and density at 2400. Cubic feet reads 53.33 ft³. Before the extra percent reads 53.33 ft³. Cubic yards reads 1.98 yd³. Cubic meters reads 1.51 m³. Short tons reads 4.00 short tons. Kilograms reads 3,624.56 kg. Bags reads 89.
Why do the yards show 1.98 when 53.33 divided by 27 is 1.975?
The panel divides the unrounded product, 20 × 4 × (8 ÷ 12) = 160 ÷ 3 cubic feet, by 27. That quotient is 1.975308…, and the yard line rounds it to 1.98. Dividing the already rounded 53.33 by 27 is 1.975, which still rounds to 1.98, but the line does not use the rounded cubic feet.
What if I switch the profile to a rectangular curb?
Set Profile to Curb, rectangle and leave every number where it opened. Cubic feet still reads 53.33 ft³. Before the extra percent still reads 53.33 ft³. Cubic yards still reads 1.98 yd³. Cubic meters still reads 1.51 m³. Short tons still reads 4.00 short tons. Kilograms still reads 3,624.56 kg. Bags still reads 89. The curb label uses the same three dimensions as the wall.
How much concrete is a 20 ft trapezoid curb, 6 in high, 6 in on top and 12 in at the bottom?
Set Profile to Curb, trapezoid. Leave length at 20 ft. Set height to 6 in. Leave top width at 6 in and bottom width at 12 in. Leave extra percent at 0, yield at 0.60, and density at 2400. Cubic feet reads 7.50 ft³. Before the extra percent reads 7.50 ft³. Cubic yards reads 0.28 yd³. Cubic meters reads 0.21 m³. Short tons reads 0.56 short tons. Kilograms reads 509.70 kg. Bags reads 13.
What does an extra 10 percent do to the opening wall?
Return to Wall, rectangle with 20 ft, 4 ft, and 8 in. Set extra percent to 10. Cubic feet reads 58.67 ft³. Before the extra percent stays 53.33 ft³. Cubic yards reads 2.17 yd³. Cubic meters reads 1.66 m³. Short tons reads 4.39 short tons. Kilograms reads 3,987.01 kg. Bags reads 98.
What if the yield box or the density box is cleared?
On the opening wall, clear the yield box. Cubic feet still reads 53.33 ft³ and cubic yards still reads 1.98 yd³. Bags reads Enter a yield. Clear the density box instead, and put 0.60 back in the yield. Short tons reads Enter a density. Kilograms reads Enter a density. Bags reads 89 again.
What is 6 m long, 1.2 m high, and 200 mm thick?
Set Profile to Wall, rectangle. Set length to 6 m, height to 1.2 m, and thickness to 200 mm. Set extra percent back to 0 if you changed it, and leave yield at 0.60 and density at 2400. Cubic feet reads 50.85 ft³. Before the extra percent reads 50.85 ft³. Cubic yards reads 1.88 yd³. Cubic meters reads 1.44 m³. Short tons reads 3.81 short tons. Kilograms reads 3,456.00 kg. Bags reads 85.