Concrete Calculator

Enter your project's length, width, and thickness to calculate exactly how much concrete you need. Choose your shape type — slab, footing, or column — and the tool returns cubic yards, cubic feet, and the number of pre-mix bags (40 lb, 60 lb, and 80 lb) required. You can also add a quantity for multiple identical sections and see a cost estimate if you enter a price per cubic yard.

Select the shape that best matches your project.

ft

Length of the slab or footing in feet.

ft

Width of the slab or footing in feet.

in

Standard residential slab thickness is 4 inches.

in

Outer diameter for round columns or circular slabs (in inches).

in

Height or depth for round column/footing in inches.

Enter how many identical slabs, columns, or footings you need.

$/yd³

Enter the cost of ready-mix concrete per cubic yard to estimate total cost.

Results

Volume (Cubic Yards)

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Volume (Cubic Feet)

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40 lb Bags Needed

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60 lb Bags Needed

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80 lb Bags Needed

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Estimated Concrete Cost

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Bag Options Breakdown (cubic yards equivalent)

Frequently Asked Questions

How do I calculate how much concrete I need?

Multiply the length, width, and thickness of your project area to get the volume in cubic inches or feet, then convert to cubic yards by dividing by 27. For round shapes, use the formula π × radius² × height. This calculator handles all the math for slabs, columns, and circular forms automatically.

What is the standard thickness of a concrete slab?

For most residential applications like driveways and patios, 4 inches is the standard thickness. Structural or heavy-load slabs (such as garage floors or commercial pads) typically require 6 inches or more. Footings and foundations may require 8–12 inches depending on local building codes.

How much does 1 cubic yard of concrete weigh?

One cubic yard of concrete weighs approximately 4,000 pounds (about 2 tons). This can vary slightly based on the mix design, aggregate type, and moisture content. Keep this in mind when planning delivery and site access for large pours.

How many bags of concrete are in one cubic yard?

One cubic yard of concrete requires approximately 45 bags of 80 lb concrete mix, 60 bags of 60 lb mix, or 90 bags of 40 lb mix. All yields are approximate — actual coverage may vary slightly based on the specific product and mixing method.

How much extra concrete should I order?

It's generally recommended to order 5–10% more concrete than your calculated volume to account for spillage, uneven subgrades, and mixing losses. For critical structural pours, err on the higher side. Running short mid-pour can cause cold joints and structural weaknesses.

Should I use bagged concrete or ready-mix delivered by truck?

For small projects under about 1 cubic yard, bagged concrete is cost-effective and convenient. For larger projects — typically anything over 1 yard — ordering ready-mix from a concrete supplier is more economical and ensures a consistent mix quality throughout the pour.

How much concrete do I need for a 10×10 slab?

A 10 ft × 10 ft slab at the standard 4-inch thickness requires approximately 1.23 cubic yards of concrete. At 6 inches thick, that same slab would need about 1.85 cubic yards. Always add a small buffer for waste and spillage.

How long does concrete take to cure?

Concrete reaches about 70% of its full strength within 7 days and achieves full design strength at 28 days. You can typically walk on it after 24–48 hours and drive on it after about a week, though curing continues for months. Keep it moist during the first week for best results.

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