DIY CalculatorThe default adds 10% for spillage and uneven subgrade — ready-mix trucks charge extra for short loads, so ordering a little over is normal.
How much concrete do you need?
- Sidewalks and patios: 4 inches thick.
- Driveways: 5–6 inches.
- Under about 1 cubic yard, bags are usually easier than a truck.
- An 80 lb bag makes about 0.60 cubic feet of concrete.
How much concrete for common areas (cubic yards / tons, no extra added)
| Area | 4 in deep | 5 in deep | 6 in deep |
|---|---|---|---|
| 100 sq ft | 1.23 yd³ / 2.5 t | 1.54 yd³ / 3.13 t | 1.85 yd³ / 3.75 t |
| 200 sq ft | 2.47 yd³ / 5 t | 3.09 yd³ / 6.25 t | 3.7 yd³ / 7.5 t |
| 500 sq ft | 6.17 yd³ / 12.5 t | 7.72 yd³ / 15.63 t | 9.26 yd³ / 18.75 t |
| 1,000 sq ft | 12.35 yd³ / 25 t | 15.43 yd³ / 31.25 t | 18.52 yd³ / 37.5 t |
Tons assume 4,050 lb per cubic yard. Add extra for waste and settling when you order.
How to use this calculator
- Measure the length and width (or the diameter of a round area). Use any unit — feet, inches, yards or meters.
- Split odd shapes into rectangles, circles and triangles, and add each one with “Add another area”.
- Enter the depth. Results update as you type: cubic yards, tons and bags.
- Optionally enter a price to estimate the cost.
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Frequently asked questions
How many bags of concrete are in a yard?
About 45 bags of 80 lb, 60 bags of 60 lb, or 90 bags of 40 lb — before adding extra for waste.
How much concrete do I need for a 10×10 slab?
At 4 inches thick, 33.3 cubic feet — 1.23 cubic yards, or about 1.36 cubic yards with 10% extra.
How thick should a concrete slab be?
Four inches is standard for patios and walkways; driveways and garage floors are usually 5–6 inches. Follow local code for structural work.