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QUANTITY WORKSHEET / 01

Concrete calculator

Calculate concrete volume in cubic feet, yards or meters and round to bags using your chosen thickness and product yield.

How to use this calculator
  1. Measure non-overlapping sections; enter a known footprint if you already have its area.
  2. Enter the thickness already chosen for your project and the finished yield on your exact bag. Different thicknesses need separate estimates.
  3. Calculate volume and bags. Compare a different bag yield only when it describes the same chosen mix.
Material quantity calculator

Your measurements

Units

Example values are loaded. Replace them with your measurements and product details.

Measurement method
Deduct a door, window or rectangle

Adds width × height × count to this area’s exclusions, per identical copy. Do not deduct it twice.

MATERIAL & ALLOWANCES

Quantity only. Thickness is your input, never a structural recommendation.

From measured volume to bag quantity

This worksheet calculates concrete volume from rectangular or circular areas and a thickness you supply. Break an irregular footprint into non-overlapping shapes. Areas in one estimate share a thickness and product yield; make a separate estimate when either changes.

The extra material allowance is applied to the total geometric volume. Bag count uses the finished yield on the exact mix label, not the dry weight of a bag. A 60-pound bag and a 60-liter bag describe different properties and cannot be substituted.

Rectangle area = length × width − excluded area Circle area = π × diameter² / 4 − excluded area Volume = sum(area × copies) × chosen thickness Adjusted volume = volume × (1 + allowance / 100) Bags = round up(adjusted volume / finished yield per bag)

Understand the inputs

Thickness
Enter an already chosen dimension. The example is not a recommendation for a slab, foundation, path or load. Use one thickness per estimate.
Yield per bag
Volume produced after mixing, expressed in cubic feet or liters. Use the manufacturer’s yield for that exact bag and formulation.
Excluded area
A footprint deducted from each copy before multiplying by thickness. It cannot equal or exceed the footprint being measured.
Allowance
An explicit percentage for the additional volume you choose to include. The calculator does not select an allowance for uneven excavation or spills.

Example: two measured sections

Suppose two rectangular sections are each 6 ft × 4 ft, with a thickness already specified as 3 in. Their combined area is 48 ft² and volume is 12 ft³. With a user-selected 5% allowance, the total becomes 12.6 ft³. If the chosen product yields 0.6 ft³ per bag, the estimate is exactly 21 bags. These inputs illustrate arithmetic only.

Common estimating mistakes

  • Using inches as though they were feet when entering thickness. The thickness field is labeled separately.
  • Dividing volume by bag weight rather than mixed yield.
  • Overlapping two measured rectangles and counting their intersection twice.
  • Assuming that bag rounding includes an extra material allowance; these are different steps.

What this estimate leaves out

No strength, reinforcement, subgrade, load, curing, mixing-water or structural suitability is determined. Different mix products stay separate in the shopping list. The estimate does not certify that the selected thickness or concrete is appropriate.

Product information & references

Manufacturer yield is product-specific. QUIKRETE links its product data sheets and notes the limitations of approximate yields. Enter your own product’s current values.