How many cubic yards of concrete do I need?
Measure length and width in feet, enter thickness in inches, then divide the cubic-foot volume by 27. For example, a 10 x 10 ft slab at 4 inches thick is about 1.23 cubic yards before waste. A 20 x 20 ft patio at 4 inches thick is about 4.94 cubic yards before waste.
What does 1 cubic yard of concrete cover?
One cubic yard is 27 cubic feet. At 4 inches thick, it covers about 81 square feet. At 5 inches thick, it covers about 65 square feet. At 6 inches thick, it covers about 54 square feet.
Common concrete project sizes in cubic yards
A 10 x 10 ft slab at 4 inches thick is about 1.23 cubic yards. A 10 x 20 ft patio at 4 inches thick is about 2.47 cubic yards. A 12 x 12 ft shed floor at 4 inches thick is about 1.78 cubic yards. A 16 x 40 ft driveway at 4 inches thick is about 7.90 cubic yards. A 24 x 24 ft garage floor at 4 inches thick is about 7.11 cubic yards. These examples do not include waste.
Ready-mix vs bagged concrete
For larger pours, ready-mix is usually planned in cubic yards. For small pours, bagged concrete can be practical. A common planning yield is about 0.60 cubic feet for an 80 lb bag and about 0.45 cubic feet for a 60 lb bag, but the product label is the source of truth.
Common concrete slab sizes
Cubic yards below are before waste. Add your project waste percentage before ordering.
| Slab size | 4 in thick | 5 in thick | 6 in thick |
|---|---|---|---|
| 10 ft x 10 ft | 1.23 cu yd | 1.54 cu yd | 1.85 cu yd |
| 10 ft x 12 ft | 1.48 cu yd | 1.85 cu yd | 2.22 cu yd |
| 12 ft x 12 ft | 1.78 cu yd | 2.22 cu yd | 2.67 cu yd |
| 20 ft x 20 ft | 4.94 cu yd | 6.17 cu yd | 7.41 cu yd |
| 24 ft x 24 ft | 7.11 cu yd | 8.89 cu yd | 10.67 cu yd |
| 30 ft x 40 ft | 14.81 cu yd | 18.52 cu yd | 22.22 cu yd |
Before you calculate
- Measure the actual formed length and width in feet.
- Enter slab thickness in inches, then handle thickened edges or footings as separate estimates.
- Break irregular slabs into rectangles so the volume calculation stays transparent.
Common mistakes
- Using square feet without converting thickness into volume.
- Missing thickened edges, turndowns, steps, or separate pads.
- Ordering exactly the calculated amount with no allowance for site variation.
Formula
cubic yards = (length * width * (thickness / 12) / 27) * (1 + wastePercent / 100)
Assumptions
- Thickness is entered in inches.
- The estimate assumes a rectangular area.
- Use actual project dimensions for final ordering.
Example
Estimated concrete needed (cubic yards): 2.22 cubic yards
How to use this calculator
- Enter length in ft.
- Enter width in ft.
- Enter thickness in in.
- Enter waste in %.
- Review the live estimate and compare it with the example result.
- Check the formula, assumptions, product labels, and site conditions before using the Cubic Yard Calculator result to plan materials.
Before you buy materials
- Compare cubic yards, cubic feet, and bag counts before deciding between ready-mix and bags.
- Confirm final slab details with plans, product labels, or a qualified professional when accuracy matters.
FAQ
What is the example cubic yard cubic-yard result?
Use length, width, thickness or depth, and waste, then calculate the planning result. In the default example, the result is 2.22 cubic yards.
How many cubic yards of concrete do I need?
It depends on length, width, and thickness. Use cubic yards = (length x width x (thickness / 12)) / 27. A 10 x 10 ft slab at 4 inches thick needs about 1.23 cubic yards before waste, while a 20 x 20 ft patio at 4 inches thick needs about 4.94 cubic yards before waste.
How many cubic yards is a standard bag of concrete?
Using common planning yields, one 80 lb bag is about 0.022 cubic yards, or 0.60 cubic feet. One 60 lb bag is about 0.017 cubic yards, or 0.45 cubic feet. Always verify the yield on the actual bag.
How much does 1 cubic yard of concrete cost?
Concrete pricing varies by location, supplier, delivery, short-load fees, mix, and project timing. Use the page's planning reference only as a rough context, then confirm current local pricing with a ready-mix supplier.
What is the minimum order for ready-mix concrete?
Minimum ready-mix orders and short-load fees vary by supplier. Many small pours can be priced differently from larger truck deliveries, so ask the supplier about minimums before deciding between ready-mix and bags.
How many square feet does 1 cubic yard of concrete cover?
One cubic yard covers about 81 square feet at 4 inches thick, 65 square feet at 5 inches thick, and 54 square feet at 6 inches thick. Divide 27 cubic feet by the slab thickness in feet to estimate coverage.
How do I convert cubic yards to cubic feet for concrete?
Multiply cubic yards by 27. For example, 2.22 cubic yards is 59.94 cubic feet. This works because one cubic yard equals 3 ft x 3 ft x 3 ft, or 27 cubic feet.
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This calculator is for planning estimates only. Verify final quantities with product labels, project conditions, and a qualified professional when accuracy matters.