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Concrete Calculator for 20x20 Slab (4" Depth)

For a 20' x 20' slab with 4" depth, you need 4.94 cubic yards of ready-mix concrete.

Concrete Slab Estimator

Calculate cubic yards, cubic feet, and 60lb/80lb premixed bags.

Cubic Yards
4.94 yd³
Cubic Feet
133.3 ft³
Premix Bags
~223 80lb / ~297 60lb

Step-by-Step Worked Explanation

Volume = 20 x 20 x (4/12) = 133.3 cubic feet. Cubic Yards = 133.3 / 27 = 4.94 yards. 80lb Bags = 223 bags.
Mathematical FormulaLaTeX Standard
\text{Cubic Yards} = \frac{L \times W \times D}{27}

Explanation: Length (ft) times Width (ft) times Depth (ft) divided by 27 cubic feet per cubic yard.

Frequently Asked Questions

How many 80lb bags for a 20x20 slab?

You will need approximately 223 bags of 80lb premixed concrete.

Need a different variation or custom calculation?

Open the full interactive Concrete Calculator tool.

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