Why Use This Calculator?
Concrete is ordered in cubic yards and mixed by the bag, and converting between the two is where DIY pours go wrong. This calculator does both: enter length, width, and thickness, and get cubic yards for the ready-mix truck or the exact 80-lb bag count for a wheelbarrow weekend.
Add about 5–10% extra to any pour — grades aren't perfectly flat and nobody wants a cold joint where the truck ran out. For anything over roughly two yards, ordering ready-mix beats mixing bags by hours.
How It Works
- Measure the slab's length and width, and set the thickness in inches.
- Read cubic yards for a ready-mix order, or the bag count for DIY mixing.
- Order 5–10% extra to cover grade variation and spillage.
Frequently Asked Questions
How many 80-lb bags of concrete make a cubic yard?
About 45 — an 80-lb bag yields roughly 0.6 cubic feet, and a yard is 27 cubic feet. The calculator converts your slab directly into bags.
What thickness should a concrete driveway be?
Four inches with reinforcement suits most residential driveways; five to six inches is wise for trucks or poor soil. Patios and walkways are typically four inches.
How do I calculate cubic yards of concrete?
Length × width × thickness in inches, divided by 324 — that's the cubic-yard shortcut. The tool applies the same formula and adds the bag conversion.
Tips & Things to Watch
- Bags for anything past ~1.5 cubic yards will test your friendships — order ready-mix.
- Wet the subgrade before pouring so the soil doesn't suck water from the mix.
- One cubic yard of concrete weighs about two tons. Plan the wheelbarrow routes accordingly.