How much concrete do I need for a 10x10 slab?

For a 10×10 foot slab at 4 inches thick, you need about 1.24 cubic yards of concrete. The calculation is: 10 ft × 10 ft × (4/12) ft = 33.33 cubic feet ÷ 27 = 1.24 cubic yards. With a 10% waste factor, order about 1.36 cubic yards. This equals approximately 56 bags of 80-lb concrete mix.

How many bags of concrete do I need per cubic yard?

One cubic yard of concrete equals 27 cubic feet. An 80-lb bag of concrete mix covers about 0.60 cubic feet, so you need approximately 45 bags of 80-lb mix per cubic yard. For 60-lb bags (0.45 cu ft each), you need about 60 bags. For 40-lb bags (0.30 cu ft each), you need about 90 bags.

How thick should a concrete slab be?

Standard concrete slab thickness is 4 inches for patios, walkways, and residential floors. Driveways should be 5-6 inches thick. Garage floors and areas with heavy loads need 6-8 inches. Footings for walls and posts are typically 8-12 inches deep and should extend below the frost line in cold climates.

Should I add extra concrete for waste?

Yes, always order 10% more concrete than calculated. Waste occurs from uneven ground, spillage, over-excavation, and form irregularities. For complex shapes or sloped ground, consider ordering 15% extra. It is much better to have a little extra than to run short during a pour, which can cause weak joints.

Is it cheaper to buy bags or ready-mix concrete?

For small projects under 1 cubic yard, bags are usually more economical and practical. At about $5-7 per 80-lb bag, one cubic yard costs roughly $225-315 in bags. Ready-mix delivery typically costs $125-175 per cubic yard but has minimum order requirements (usually 1 yard) and delivery fees ($50-100+). For projects over 2 cubic yards, ready-mix is generally cheaper and much faster.

How do I calculate concrete for a round column?

Use the formula: Volume = π × radius² × height. For a 12-inch diameter column that is 4 feet tall: radius = 0.5 ft, so Volume = 3.14159 × 0.25 × 4 = 3.14 cubic feet = 0.116 cubic yards. You would need about 6 bags of 80-lb mix. For tube forms (sonotubes), measure the inner diameter.

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To calculate concrete needed: multiply length × width × depth to get volume. A 10×10 ft slab at 4 inches thick needs 1.24 cubic yards (33.3 cu ft ÷ 27). One cubic yard requires about 45 bags of 80-lb mix, 60 bags of 60-lb mix, or 90 bags of 40-lb mix. Always add 10% for waste.

Calculate how much concrete you need for slabs, patios, footings, columns, walls, and stairs. Get volume in cubic yards, cubic feet, and cubic meters. See bags needed (40, 60, 80 lb) and cost estimates. Supports multiple sections, 10% waste factor, and imperial/metric units.

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Frequently Asked Questions

How much concrete do I need for a 10x10 slab?: For a 10×10 foot slab at 4 inches thick, you need about 1.24 cubic yards of concrete. The calculation is: 10 ft × 10 ft × (4/12) ft = 33.33 cubic feet ÷ 27 = 1.24 cubic yards. With a 10% waste factor, order about 1.36 cubic yards. This equals approximately 56 bags of 80-lb concrete mix.
How many bags of concrete do I need per cubic yard?: One cubic yard of concrete equals 27 cubic feet. An 80-lb bag of concrete mix covers about 0.60 cubic feet, so you need approximately 45 bags of 80-lb mix per cubic yard. For 60-lb bags (0.45 cu ft each), you need about 60 bags. For 40-lb bags (0.30 cu ft each), you need about 90 bags.
How thick should a concrete slab be?: Standard concrete slab thickness is 4 inches for patios, walkways, and residential floors. Driveways should be 5-6 inches thick. Garage floors and areas with heavy loads need 6-8 inches. Footings for walls and posts are typically 8-12 inches deep and should extend below the frost line in cold climates.
Should I add extra concrete for waste?: Yes, always order 10% more concrete than calculated. Waste occurs from uneven ground, spillage, over-excavation, and form irregularities. For complex shapes or sloped ground, consider ordering 15% extra. It is much better to have a little extra than to run short during a pour, which can cause weak joints.
Is it cheaper to buy bags or ready-mix concrete?: For small projects under 1 cubic yard, bags are usually more economical and practical. At about $5-7 per 80-lb bag, one cubic yard costs roughly $225-315 in bags. Ready-mix delivery typically costs $125-175 per cubic yard but has minimum order requirements (usually 1 yard) and delivery fees ($50-100+). For projects over 2 cubic yards, ready-mix is generally cheaper and much faster.
How do I calculate concrete for a round column?: Use the formula: Volume = π × radius² × height. For a 12-inch diameter column that is 4 feet tall: radius = 0.5 ft, so Volume = 3.14159 × 0.25 × 4 = 3.14 cubic feet = 0.116 cubic yards. You would need about 6 bags of 80-lb mix. For tube forms (sonotubes), measure the inner diameter.

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