How do I calculate concrete yards?

Multiply length by width to get square feet, multiply by thickness in feet to get cubic feet, then divide by 27 for cubic yards. Add 5% to 15% waste before ordering.

How many 80 lb bags of concrete are in a cubic yard?

An 80 lb bag yields about 0.6 cubic feet, so one cubic yard takes about 45 bags before waste. Larger projects are usually cheaper with ready-mix delivery.

How thick should concrete be for a driveway?

Many residential driveways use 4 to 5 inches of concrete over a prepared base. Heavy vehicles, poor soil, or local code may require thicker concrete and reinforcement.

Should I order concrete by bags or ready-mix?

Bags work for small pads, repairs, and post bases. Ready-mix is usually better for driveways, large slabs, and projects above one or two cubic yards.

How much extra concrete should I order?

Order about 10% extra for most slabs. Increase the waste allowance for uneven subgrade, forms that are hard to measure, deep edges, or hand-mixed bag projects.

Concrete yard and bag estimator

Free Concrete Calculator

A concrete calculator estimates how much concrete you need from project length, width, thickness, waste, and local prices. Use it to plan slabs, driveways, patios, footings, and post-base layouts before buying bags or ordering ready-mix.

Project details

Project typeBag sizeLength

Width

Thickness

Waste allowance

Price per bag

Ready-mix price

$/cu yd

Small pours

Use bag estimates for post bases, stair repairs, small pads, and projects where delivery minimums are too expensive.

Larger slabs

Compare ready-mix pricing when the result is above one or two cubic yards, especially for driveways and patios.

Order buffer

Keep the waste allowance on unless your forms are exact and the subgrade is flat. Running short during a pour is costly.

Concrete calculator FAQ

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