Concrete Calculator

Calculate cubic yards and bags of concrete for your slab project. Works for patios, walkways, driveways, and shed bases.

🧱 Enter Your Slab Dimensions

4 in is standard for patios and walkways

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How to Calculate Concrete Volume

Our concrete calculator helps you estimate cubic yards and bags of concrete for your slab project. Multiply the slab length by the width and the thickness in feet to get cubic feet, then divide by 27 for cubic yards. We add 10% waste to cover spillage, uneven subgrade, and over-excavation.

Slab Thickness Guidelines

  • 3 inches: Light foot traffic only, such as small pads
  • 4 inches: Standard for patios, walkways, and shed bases
  • 5 inches: Driveways with regular passenger vehicles
  • 6 inches: Driveways with trucks, RVs, or heavy loads

Bags vs Ready-Mix Concrete

Bagged concrete works well for small projects like footings, post holes, and pads under 1 cubic yard. An 80lb bag yields about 0.60 cubic feet, so a full cubic yard takes roughly 45 bags. For anything larger, ready-mix delivery is usually cheaper per yard, arrives consistently mixed, and saves hours of hand mixing.

Frequently asked questions

How much concrete does an 80lb bag make?⌄
An 80lb bag of concrete mix yields approximately 0.60 cubic feet of concrete. That works out to roughly 45 bags per cubic yard, which is why bagged concrete is best suited to smaller slabs and footings.
How thick should a concrete patio slab be?⌄
A 4 inch thick slab is the standard for patios and walkways. If the slab will support vehicles, such as a driveway or parking pad, increase the thickness to 5 to 6 inches.
How many bags of concrete do I need for a 10x10 slab?⌄
A 10x10 slab at 4 inches thick requires about 1.23 cubic yards of concrete including waste, which is roughly 75 80lb bags. At that volume, ordering ready-mix concrete is usually the better option.
Should I order ready-mix or use bags?⌄
For projects over about 1 cubic yard, ready-mix delivery is typically cheaper and far easier than mixing dozens of bags by hand. Bags make sense for small slabs, footings, and post holes.
How long does concrete take to cure?⌄
Concrete is typically walkable within 24 to 48 hours, but it continues to gain strength over time and reaches its full design strength after about 28 days. Keep it moist during the first week for the best result.

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