Home / Home & Construction / Concrete Bag Calculator
Home & Construction

How Many Bags of Concrete Do I Need?

Check thickness changes before buying bags ↓

Start with cubic yards, cubic feet, or rectangular slab dimensions. Use the yield printed on your exact mix, add the allowance your project needs, and turn the result into a shopping worksheet.

Quick answer · one cubic yard45 80-lb bags before extraAt 0.60 ft³ per bag: 27 ÷ 0.60 = 45. With 10% extra, round 49.5 up to 50 whole bags. At 0.45 ft³ per 60-lb bag, the same yard takes 60 bags before extra.Calculate your quantity →
  1. 1. Enter volume or dimensions
  2. 2. Review your shopping worksheet
Quantity planning only—not structural design or a thickness recommendation. Verify the exact product yield, measurements and placement requirements before buying.
Updated October 14, 2026Runs in your browser

1. Calculate your bag quantity

Editable allowance, not a universal requirement.

Which concrete tool fits your question?

Patio purchase planner: compare bagged mix with a complete ready-mix quote, order increments and delivery fees.

How this calculator works

Bags = required cubic feet × (1 + waste percentage) ÷ yield per bag, rounded up to a whole bag.

How many concrete bags make one cubic yard?

One cubic yard is 27 cubic feet. At a 0.60-cu-ft yield, it takes 45 80-lb bags; at a 0.45-cu-ft yield, it takes 60 60-lb bags. Those counts exclude extra material. With 10% extra, round up to 50 80-lb bags or 66 60-lb bags.

Choose 1 cubic yard or 27 cubic feet to check that example. Choose custom yield if your product lists a different volume. For a 10 × 10 slab at 4 inches thick, first calculate 33.33 cubic feet; the area alone does not determine the bag count.

Use the yield printed on the exact bag

Bag weight is not a universal volume. Standard concrete mix, fast-setting mix, repair products, and specialty formulations can produce different yields at the same weight. Replace the default yield with the manufacturer’s published value when it differs.

Calculate the required wet volume from the project dimensions first. Round fractional results up because partial bags are impractical for purchasing and mix consistency.

Decide when bags stop being practical

Bagged mix is convenient for small, distributed placements, but labor and mixing capacity become important as quantity grows. Compare the number of batches, water control, mixer output, placement time, and ready-mix minimum charges before choosing a method.

Sources & assumptions

The selectable 60-lb and 80-lb yields follow QUIKRETE Concrete Mix product data. Other products can have different yields.

Frequently asked questions

Why use the bag’s listed yield?

Mix designs and bag sizes vary. The manufacturer’s yield is more reliable than a generic conversion.

Can I use this for fence posts?

Yes, after calculating the total hole volume. Subtract post volume if the post occupies a meaningful part of each hole.

Related calculators

Concrete CalculatorEstimate concrete volume, ready-mix yards, and bag quantities for rectangular or circular projects.Open →Post Hole Concrete CalculatorEstimate 60- and 80-pound concrete bags for round fence post holes using hole diameter, depth, post size, quantity, and extra material.Open →Concrete Footing CalculatorCalculate concrete yards and bag quantities for rectangular strip, wall, or repeated footings using editable dimensions and waste.Open →How many bags of concrete do I need?Turn cubic feet into whole bags using manufacturer-listed yield and a practical extra-material allowance.Read guide →
Original measurement check · October 17, 2026

What does a quarter-inch thickness difference change?

A uniform-depth estimate can hide a meaningful quantity difference. For a hypothetical 10 × 10 ft footprint, 0.60 ft³ per bag and 10% extra, 3.75 in thickness needs 58 bags, 4 in needs 62, and 4.25 in needs 65. These are arithmetic scenarios, not recommended slab thicknesses.

3.75 in4 in4.25 in58 bags62 bags65 bags

This is not a probability range. It models three uniform thicknesses across the whole footprint. For a varying subgrade, measure separate areas and depths, add their volumes, then apply an explicit allowance once. Extra material cannot fix a structurally unsuitable slab or a poorly measured base.

Product-label and ordering checklist
  1. Record the exact product name, bag size, published yield and date of your price. Bag weight alone is not coverage.
  2. Keep measured volume, allowance and whole-bag rounding separate. Do not add the same allowance again to the rounded purchase.
  3. Compare the complete bag purchase with a ready-mix quote, including minimums, order increments, handling and equipment.
  4. Have the required slab section and installation requirements confirmed independently. This check does not choose mix, thickness, reinforcement or placement methods.

The 0.60 ft³ example is supported by QUIKRETE Concrete Mix product 1101 data, checked October 17, 2026; other mixes may differ. NRMCA CIP 8 explains why field geometry and yield need separate checks.

Compare bagged and ready-mix purchase scenarios · Inspect the calculation checks