Concrete Calculator — Free Online Concrete Calculator

Estimate concrete in cubic yards and bags for a slab or patio. 100% free, no signup.

Concrete needed
0 yd³
Volume0 ft³
Bags (incl. 5%)0
Slab—

How much concrete do I need?

Multiply width × length × thickness (in feet) to get cubic feet, then divide by 27 for cubic yards. Ready-mix is ordered by the cubic yard; bagged concrete covers a fixed volume each (a 60 lb bag ≈ 0.45 ft³, an 80 lb bag ≈ 0.60 ft³). Add about 5–10% extra.

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Frequently asked questions

Bags or ready-mix?

For small slabs, patios and footings, bags are convenient. For anything over about half a cubic yard, ready-mix delivery is usually cheaper and easier.

How thick should a patio be?

A typical patio slab is 4 inches thick; driveways and areas with heavy loads are often 5–6 inches.

Designing the outdoor space?

Download RoomGPT free and reimagine your patio, garden or exterior with AI from a photo.