Concrete calculator
Enter the length, width and thickness of your pour and this calculator gives you the volume in cubic yards and cubic feet, the number of 40, 60 or 80 lb bags, and a rough ready-mix cost. It adds a small waste allowance so you don't come up short. Concrete is sold by the cubic yard delivered, or in bags for small jobs.
Ready-mix ballpark: $170–$238 for the concrete delivered (materials only, before labor). Past ~1 cubic yard, ready-mix usually beats bags on price and effort.
Estimates only — round up when you order, and confirm exact quantities and conversions with your supplier.
- ›1 cubic yard = 27 cubic feet
- ›80 lb bag ≈ 0.60 cu ft · 60 lb bag ≈ 0.45 cu ft · 40 lb bag ≈ 0.30 cu ft
- ›Add 5–10% extra for waste, spillage and uneven subgrade
- ›4 inches is standard for patios and walkways; 5–6 inches for driveways
Pouring more than a few bags? A concrete contractor is usually cheaper and flatter than mixing by hand.
Concrete calculator — frequently asked questions
How much concrete do I need?
Multiply length × width × thickness (all in feet) to get cubic feet, then divide by 27 for cubic yards. A 10×10 ft slab at 4 inches thick is about 1.23 cubic yards, or roughly 56 × 80 lb bags. Always add 5–10% for waste and spillage.
How many bags of concrete in a cubic yard?
A cubic yard is 27 cubic feet. An 80 lb bag of concrete yields about 0.6 cubic feet, so you need roughly 45 × 80 lb bags per cubic yard. For 60 lb bags it's about 60 bags, and for 40 lb bags about 90 bags.
Should I use bags or ready-mix concrete?
Bags make sense for small jobs — a few post holes or a tiny pad. Once you pass roughly 1 cubic yard (about 45 × 80 lb bags), ordering ready-mix delivered by the truck is usually cheaper, easier and gives a more consistent, monolithic pour.
How much does a yard of concrete cost?
Ready-mix concrete runs roughly $125–$175 per cubic yard delivered, before labor. Small loads and short-load fees can push the per-yard price higher. The calculator gives a materials-only ballpark — get a local quote for the poured, finished price.
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This calculator gives estimates for planning only. Round up when you order, and confirm exact quantities, coverage and weight conversions with your supplier — materials vary.