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October 13, 2026

Concrete Patio Calculator

Concrete Patio Calculator

Calculate how much concrete you need for your patio. Estimate cubic yards, cubic feet, and the number of concrete bags based on your measurements.

Enter Patio Measurements

A common patio slab thickness is 4 inches, but follow your project requirements and local building guidance.
Extra material helps account for uneven ground, spillage, and small measurement differences.
Actual bag yield varies by product. Check the manufacturer’s packaging.

Your Concrete Estimate

Concrete needed (including extra allowance)
3.26
cubic yards (yd³)
Patio area240.00 ft²
Base concrete volume2.96 yd³
Extra concrete10%
Total volume87.91 ft³
Estimated 80 lb bags147 bags
Measurements20 × 12 ft, 4 in thick
This is a planning estimate, not a structural design. For large pours, consider ready-mix delivery and confirm quantities with your concrete supplier.
Downloads only your entered measurements and calculated results in a text file.

How to Calculate Concrete for a Patio

For a rectangular patio, multiply length by width to get the area. Multiply the area by the slab thickness to find the volume. For a circular patio, use the circle’s area formula.

Rectangular patio

Volume = Length × Width × Thickness

Circular patio

Volume = π × (Diameter ÷ 2)² × Thickness

Convert cubic feet to cubic yards

Cubic yards = Cubic feet ÷ 27

Include extra concrete

Order estimate = Base volume × (1 + extra percentage ÷ 100)

Frequently Asked Questions

How much concrete do I need for a 20 × 12 patio?

For a 20 ft × 12 ft patio with a 4-inch slab, the base volume is about 2.96 cubic yards. With a 10% allowance, the estimate is about 3.26 cubic yards.

How many bags of concrete do I need for a patio?

Bag quantities depend on the slab volume, bag size, and the manufacturer’s stated yield. This calculator estimates the number of whole bags by rounding up.

How thick should a concrete patio be?

Four inches is a common starting point for many residential patios, but soil conditions, loads, reinforcement, climate, and local codes can affect the required slab design.

Should I include extra concrete?

An allowance of around 5–10% is often used for planning, depending on site conditions. Uneven ground and complicated shapes may require more.