Concrete · updated 2026
Concrete Calculator
Measure the shape, choose a waste factor, and this concrete calculator converts the result into cubic yards, equivalent 60- and 80-lb bags, and a material-cost planning figure. Use the specialized driveway, slab, footing, and rebar calculators for project-specific details; stairs are outside this first version.
4 in is common for patios; vehicles often need 5–6 in
TBD — enter your local ready-mix price per cubic yard
Show the math
Base volume depends on the selected shape; for a slab = 10 × 10 × (4 ÷ 12) ÷ 27 = 1.23 yd³
With 5% waste = 1.23 × 1.05 = 1.30 yd³
80-lb bags = 1.30 × 45 = 59; 60-lb bags = 1.30 × 60 = 78
Material cost = 1.30 yd³ × $0/yd³ = $0
How to use this concrete calculator
Choose slab, footing, or column, enter the dimensions, then add a waste factor. The results show cubic yards first because ready-mix is ordered that way, followed by equivalent bag counts for small pours.
Stairs are intentionally outside this head calculator for now; use the dedicated concrete steps calculator for stair geometry.
Ready-mix versus bags
Bags are convenient for small jobs because you can buy exactly what you can mix. Larger pours are usually easier to price as ready-mix, but minimum-load and short-load fees can change the crossover. The recommendation is a planning flag, not a quote.
Methodology and assumptions
The formulas use 27 cubic feet per cubic yard, 0.6 cubic feet per 80-lb bag, and 0.45 cubic feet per 60-lb bag. Prices, delivery, labor, reinforcement, and structural design are not included unless you enter a local price.
What the numbers mean
The calculator converts your measurements into a practical purchase quantity using a documented coverage or spacing assumption.
Any whole-unit quantity is rounded up so the result does not leave you short during the project.
Use the cost range as a planning baseline and confirm the final quantity, availability, and delivery charge with your local supplier.
2026 material prices
Ready-mix, bulk material, and labor prices are TBD; enter local prices for a planning estimate. Verify current supplier pricing. 2026 U.S. national averages. Prices vary by region and retailer — confirm locally before buying.
Pro tips
- A cubic yard is a 3×3×3-ft cube and covers about 81 sq ft at 4 in deep.
- Use 5% waste for simple forms and 10% for uneven subgrade, awkward shapes, or spillage.
- Four inches is a common patio thickness; driveways often need 4–5 in and heavier vehicles may need 5–6 in.
- Ready-mix orders can have minimum-load or short-load fees; confirm the supplier minimum before ordering.
- Concrete bags are practical for small pours, but carrying and mixing dozens of bags is real labor.
- Thickness above 8 in deserves a structural review rather than a quantity estimate alone.
Common questions
Frequently asked questions
How much concrete do I need?
Multiply square feet by thickness in feet, divide by 27 for cubic yards, then add 5–10% for waste. Enter the shape and dimensions above for the exact yard and bag equivalents.
How many bags of concrete are in a cubic yard?
One cubic yard is approximately 45 eighty-lb bags or 60 sixty-lb bags. The calculator rounds both bag counts up.
How many cubic yards for a 10×10 slab?
At 4 in thick, a 10×10 slab is 1.23 yd³ before waste and about 1.30 yd³ with the calculator’s default 5% waste; plan to buy about 1.5 yd³ from a supplier.
Is it cheaper to buy concrete by the bag or ready-mix?
Bags are usually practical below about 0.5 yd³; ready-mix is often worth pricing above that. Compare local bag, delivery, and short-load charges.
How much does a yard of concrete cost?
Ready-mix pricing is TBD and varies by region, mix, delivery, and short-load fees. Enter your local delivered price per cubic yard above.
How thick should my concrete slab be?
Four inches is common for patios and walks; vehicles often call for 5–6 inches. Follow your plans and local requirements.
What is the waste factor for concrete?
Five to ten percent covers spillage, form flex, and an uneven subgrade. Use the higher end for irregular forms.
Do I need rebar in my slab?
Reinforcement depends on the slab use, soil, loads, and local requirements. Use the rebar calculator for a material takeoff after confirming the design.
Related calculators
Planning estimates only. Prices are 2026 U.S. national averages and vary by region — confirm with your local supplier before buying.