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Concrete Calculator

Calculate concrete volume, weight, and bag requirements for slabs, footings, columns, beams, walls, stairs, cylinders, and curbs. Supports Metric and Imperial units.

CalculatorHow to CalculateFormulas & ExamplesFAQs

Select a shape, input dimensions, and click Calculate.

10%

Adds extra concrete volume for spillage and form deflection (5–10% recommended).

Calculation Results

Outputs
Awaiting Calculations

Fill in the shape dimensions and click the Calculate button to view exact volumes, weight, and bag estimates.

Formula Details

Calculation Example

How to Use

Follow these simple steps to calculate your project's concrete volume and bag requirements:

  1. Choose your unit system: Toggle between imperial (feet and inches) and metric (meters and centimeters) using the selector at the top of the calculator.
  2. Select the shape tab: Click the tab corresponding to your structure shape (Slab, Footing, Column, Beam, Wall, Stair, Cylinder, or Curb).
  3. Input dimensions: Enter the measurements for your concrete layout. Ensure values are positive numbers.
  4. Adjust quantity & wastage: Enter how many identical items you are pouring and select a waste buffer (10% is standard) to account for uneven subgrade or spills.
  5. Read results: The results panel displays the total volume, estimated weight, and the precise count of premixed concrete bags needed.

Frequently Asked Questions

How do I calculate concrete volume manually?
For rectangular shapes like slabs or footings, measure the length, width, and thickness. Convert all measurements to the same unit (e.g., feet or meters), multiply them together to get the volume, and add a 5% to 10% wastage allowance. If ordering in cubic yards, divide the cubic feet by 27.
Why should I add a wastage factor to my concrete estimate?
Poured concrete frequently experiences material loss due to uneven ground levels, spills during transport and placement, structural formwork bowing, and leftovers in mixing trucks. Adding 5% to 10% ensures you don't run out mid-pour, which can compromise structural integrity.
How much volume does a standard bag of concrete yield?
An 80 lb bag yields approximately 0.60 cubic feet of wet concrete; a 60 lb bag yields about 0.45 cubic feet; and a 40 lb bag yields 0.30 cubic feet. In metric regions, a 40 kg bag yields roughly 0.0187 cubic meters, while a 25 kg bag yields about 0.0140 cubic meters.
What is the standard density of cured concrete?
Standard weight concrete has an average dry density of approximately 150 pounds per cubic foot (lbs/ft³) or 2,400 kilograms per cubic meter (kg/m³). This is used to estimate the weight of structural columns, slabs, and beams.
How long does concrete take to cure?
Concrete typically cures to 70% of its full design strength within 7 days, and reaches standard structural maturity at 28 days. Proper hydration (moisture retention) during the first 3 to 7 days is vital to prevent shrinkage cracks.

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Disclaimer

Calculations are estimates based on the values you enter and standard engineering formulas. Results are intended for planning and estimation only. Always verify critical measurements, specifications, and local building requirements before purchasing materials or beginning construction.