Cubic Yards vs Cubic Feet: Which Number You Need
Ready-mix concrete is ordered and priced by the cubic yard. Bags are labelled and calculated in cubic feet. This calculator gives you both — use cubic yards when calling a supplier, cubic feet when counting bags.
One cubic yard equals 27 cubic feet. That conversion trips up more people than any other step in the process. Getting it wrong by a factor — ordering 27 yards instead of 1 yard — is the kind of mistake that makes a very expensive morning. The calculator handles the conversion automatically in every shape mode.
Ordering Ready-Mix: What to Tell the Dispatcher
- Volume in cubic yards — Round up to the nearest quarter yard. Dispatchers don't load fractional amounts smaller than that.
- Mix design (PSI) — Standard residential concrete is 3,000 PSI. Driveways and garage floors often spec 4,000 PSI for freeze-thaw resistance. Ask if unsure — the dispatcher can recommend based on your application.
- Slump — A measure of workability. 4–5 inch slump is standard for slabs. Tell them what you're pouring; they'll set the slump accordingly.
- Delivery window — Concrete starts setting within 90 minutes of water contact. Have your forms, reinforcement, and finishing crew ready before the truck arrives. Short-load fees (for orders under the truck minimum, typically 5–7 yards) run $50–$150.
- Fibre or no fibre — Polypropylene fibre is a cheap add-on that reduces plastic shrinkage cracking. Worth specifying for any exposed slab.
Concrete volume calculations assume a uniform thickness throughout. Tapered or stepped slabs should be broken into sections and calculated separately.
Need a different shape? The full Concrete Calculator covers slabs, footings, round columns, and post holes in one place.