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.
Worked example: a 10 × 10 ft area, 4 inches deep
- Area: 10 × 10 = 100 square feet.
- Convert depth to feet, then multiply: 100 × (4 ÷ 12) = 33.33 cubic feet, or 1.23 cubic yards.
- With a chosen 10% allowance: 33.33 × 1.10 gives 36.67 cubic feet, or 1.36 cubic yards.
- At 0.6 cubic feet per 80 lb bag, divide the unrounded volume by the yield and round up: 62 whole bags.
The dimensions and 10% allowance are an example, not a slab design or a required waste factor. Use the yield printed on the mix you buy; bag weight and wet-concrete density are different inputs.
Concrete bag yield and weight assumptions
The QUIKRETE Concrete Mix No. 1101 data sheet lists approximate yields of 0.30, 0.45 and 0.60 cubic feet for 40, 60 and 80 lb bags. Those are the bag-yield defaults used here; another mix may differ.
The calculator’s weight estimate uses a separate adjustable density of 150 lb per cubic foot. The cited product lists approximately 140 lb per cubic foot, so its yield information does not validate the default weight estimate. Enter your supplier’s density when estimating tons.
For volume conversions, see the cubic yard calculator. For the measured area, use the square footage calculator.
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.
Add this calculator to your website
Run a landscaping supply, garden center or DIY blog? Paste this code into your page to let visitors use the concrete calculator right there. It is free, has no ads, and resizes itself to fit.
More calculators
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.