Concrete Calculator
Add slabs, footings or round holes to estimate cubic yards and concrete mix bags.
Use your specified pour dimensions
| Job | Dimensions to use |
|---|---|
| Slab | Use the thickness specified for your project |
| Footing | Use the designed width and depth |
| Round hole or column | Enter full pour depth; no post displacement is deducted |
Enter dimensions from your plans. This calculator does not specify structural thickness, footing design or reinforcement.
How much does a cubic yard of concrete cover?
One cubic yard is 27 cubic feet. Spread it 1 inch deep and it covers 324 square feet. Every extra inch of depth cuts the coverage proportionally. A cubic yard of concrete weighs about 1.89 tons.
| Depth | 1 cubic yard covers |
|---|---|
| 1 in | 324 sq ft |
| 2 in | 162 sq ft |
| 3 in | 108 sq ft |
| 4 in | 81 sq ft |
| 6 in | 54 sq ft |
How the concrete calculator works
Area = length × width (round hole: π × radius²)
Cubic feet = area × (depth in inches ÷ 12) × count
Cubic yards = cubic feet ÷ 27
Tons = cubic yards × weight per cubic yard ÷ 2,000
Worked example: a 10 × 10 ft slab, 4 in thick
Area: 10 × 10 = 100 sq ft. Volume: 100 × (4 ÷ 12) = 33.3 cubic feet. Cubic yards: 33.3 ÷ 27 = 1.23 cubic yards, which weighs about 2.33 tons at 3,780 lb per cubic yard.
Adding 10% as an allowance brings it to 1.36 cubic yards, about 2.57 tons. Concrete is usually sold by the cubic yard or as bags of dry concrete mix.
Tips before you order
- Use your plans for thickness, footings and reinforcement. This is a quantity estimate, not a structural design.
- Extra is an adjustable allowance for over-excavation, spillage and variation; 10% is a starting choice, not a requirement.
- Bag yields shown follow QUIKRETE Concrete Mix 1101. Other mixes can yield differently: check the label.
- Ready-mix minimums and order increments vary. Confirm your calculated quantity with the supplier.
Sources and assumptions
Bag counts use mixed yield and the volume including extra, before ready-mix rounding. Compare alternative bag sizes; do not add the bag counts together. Round holes count their full volume without subtracting a post.
Questions people ask
How much does a cubic yard of concrete weigh?
The default is 3,780 lb per cubic yard, based on the cited Mix 1101 unit weight. Other mixes and reinforcement change weight. Ask your supplier and edit the weight field.
How many square feet does a yard of concrete cover?
One cubic yard covers 162 sq ft at 2 inches deep, 108 sq ft at 3 inches and 81 sq ft at 4 inches. The rule: 324 ÷ depth in inches.
How do I convert cubic yards of concrete to tons?
Multiply cubic yards by the weight per cubic yard and divide by 2,000. At 3,780 lb per yard, that's cubic yards × 1.89.
How many 80 lb bags of concrete are in a cubic yard?
About 45 80 lb bags make one cubic yard (by volume).
How many 60 lb bags of concrete are in a cubic yard?
About 60 60 lb bags make one cubic yard (by volume).
How many 40 lb bags of concrete are in a cubic yard?
About 90 40 lb bags make one cubic yard (by volume).
How much concrete do I need for a 10 × 10 ft slab, 4 in thick?
About 1.23 cubic yards (about 2.33 tons), or 1.36 cubic yards with 10% extra for settling.