Free estimate — verify against local code before building
Concrete Bags Calculator
Choose a shape, enter its size, and get whole concrete bags using a visible yield assumption.
What this calculator includes
Enter a rectangular or circular pour—or a volume you already know—to estimate whole concrete bags. The calculator shows the exact volume, adds your waste allowance, and uses an editable product-label yield so the order matches the mix you plan to buy.
How to use this concrete bags calculator
- 01
Choose the project shape
Use a rectangle for slabs and pads, a circle for round pads, or enter a known cubic-foot volume.
- 02
Measure finished dimensions
Enter the planned length, width or diameter, and concrete thickness—not the excavation size.
- 03
Match the bag label
Select the bag weight and replace the default yield if the manufacturer's label states a different volume.
- 04
Add waste and round up
Add an allowance for uneven subgrade and handling; the result rounds up to a whole bag.
Worked example
Example: 10 × 8 ft pad
A 10 × 8 ft pad at 4 in thick contains 26.67 ft³. With 10% waste, the order is 29.33 ft³, or 49 of the 80 lb bags at an assumed 0.60 ft³ each.
Practical buying and overage guidance
Confirm bag yield and required water on the exact product label. Stage enough bags before mixing, keep them dry, and compare ready-mix delivery for pours that would require many batches.
Continue the project
Pour a Concrete Slab
Plan slab excavation, base, concrete yards or bags, forms, reinforcement allowances, delivery, labor, equipment, and contractor pricing.
Open the project workflow →Calculation sources and review
Primary references and formula assumptions are linked so you can verify them against the selected product, supplier, and adopted local requirements.
Internal formula review completed July 13, 2026. What this review covers
- QUIKRETE Concrete Mix product data (opens in a new tab)
Reference yields for common bag sizes; always verify the selected bag label.
- NRMCA — Concrete in Practice (opens in a new tab)
Concrete ordering, placement, and quality guidance.
Frequently asked questions
How much concrete does an 80 lb bag make?
A common planning yield is about 0.60 cubic feet per 80 lb bag. Mix designs differ, so use the yield printed on the product you will purchase.
How many 60 lb concrete bags are in a cubic yard?
At 0.45 cubic feet per bag, one cubic yard requires 60 bags before waste. Add the allowance appropriate for the forms and subgrade.
Should I calculate from excavation depth or concrete thickness?
Use the finished concrete thickness. Gravel base, topsoil removal, and other layers are separate from concrete volume.
When should I consider ready-mix instead of bags?
Compare delivery minimums, site access, placement time, and the labor of mixing. Larger or time-sensitive pours often justify a ready-mix quote.
Why does the calculator round up?
Concrete bags are sold whole. Rounding down leaves less mixed concrete than the entered dimensions require.