Slab, footing, or wall
Volume = length × width × depth
For a wall, height replaces width; for a slab or wall, thickness is the third dimension.
How it works
How your measurements become a concrete estimate.
We put every measurement into one consistent unit, calculate the chosen shape, then apply quantity and your allowance.
Round column
Volume = π × (diameter ÷ 2)² × height
This assumes a straight cylinder with a uniform diameter.
Post hole
Concrete = hole cylinder − embedded post
Only the section of post within the chosen embedment depth is subtracted—not the full post and not empty hole depth below it.
Waste and quantity
Amount to buy = shape volume × quantity × (1 + waste %)
No rounding is applied to the calculation; rounding occurs only when values are displayed or whole bags are counted.
Before you order
What this estimate assumes
- Dimensions describe regular shapes with a uniform depth or thickness. Irregular excavations should be measured in sections.
- The default 10% allowance is a planning starting point, not a universal rule. Spillage, uneven subgrade, form variation, and ordering method can change the appropriate allowance.
- Post-hole mode subtracts only the volume of the post actually embedded within the concrete-filled hole.
- Ready-mix suppliers may require a minimum order or use their own delivery increments. Confirm local ordering rules before purchasing.
QUIKRETE product-yield reference
Bag estimates use the approximate yields published for QUIKRETE Concrete Mix. These are identified product references, not universal yields for every concrete mix.
- 40 lb / 18.1 kg
- 0.30 ft³ / 8.5 L
- 50 lb / 22.6 kg
- 0.375 ft³ / 10.6 L
- 60 lb / 27.2 kg
- 0.45 ft³ / 12.7 L
- 80 lb / 36.2 kg
- 0.60 ft³ / 17 L
Reference: QUIKRETE Concrete Mix No. 1101 product data. Actual yield varies with mixing and placement; verify current packaging and the manufacturer’s current product data.
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