Free tool · No signup to try
Concrete Calculator
Add each slab's length, width, and thickness, get cubic feet and cubic yards per slab, apply a waste factor, then see whether a ready-mix truck or bags makes more sense — and print a clean pour sheet. Your measurements never leave this page.
Slabs
Thickness: patios & AC pads are commonly 4″; driveways commonly 4–6″. Decimals are fine everywhere.
Waste factor
Most pours order 5–10% extra for uneven subgrade and spillage — adjust to your site.
Ready-mix truck
Ready-mix is typically sold by the quarter yard — round up when you order, and ask your plant about short-load fees on small pours.
Buying bags instead?
1 cubic yard ≈ 45 80-pound bags — past about a yard, the truck usually wins. Yields per the manufacturer's data sheet.
Planning estimate — subgrade prep, forms, and reinforcement are their own jobs, and concrete work is often permitted work. Confirm quantities with your ready-mix supplier before ordering.
Live results
| Slab | L × W × Thickness | Cu Ft | Cu Yd |
|---|---|---|---|
| Slab 1 | 0 × 0 ft × 0″ | 0.00 | 0.00 |
Planning estimate — subgrade prep, forms, and reinforcement are their own jobs, and concrete work is often permitted work. Confirm quantities with your ready-mix supplier before ordering.
Frequently asked questions
How do I calculate concrete for a slab?
Multiply the slab's length by its width in feet, then by the thickness converted to feet (inches ÷ 12) — that gives you cubic feet. Divide by 27 to get cubic yards, which is how ready-mix is sold. This calculator does that for every slab, totals them, and applies a waste factor at the end.
How thick should my concrete slab be?
Patios, walkways, and AC pads are commonly poured around 4 inches thick, while driveways commonly run 4–6 inches depending on vehicle weight. Soil conditions, reinforcement, and climate all matter — check your local code and soil before you set the forms.
Should I order a ready-mix truck or buy bags?
One cubic yard is roughly 45 eighty-pound bags of concrete mix — mixing that by hand is a serious job, so past about a yard the truck usually wins. For small pads of a few cubic feet, bags are simpler and sidestep the short-load fees many plants charge on small ready-mix orders. This calculator shows both numbers so you can compare.
How much extra concrete should I order?
Most pours order about 5–10% extra to cover uneven subgrade, spillage, and form variations, since running short mid-pour costs far more than a small cushion. The right amount depends on your site and forms — adjust the waste factor here and confirm the final quantity with your ready-mix supplier.