Order 5–10% extra. Forms bulge, subgrades are never perfectly level, and coming up short mid-pour is the most expensive mistake in concrete. Tick the waste box below — it adds a 5% cushion.
How much concrete do you need?
4″ is the standard minimum for a residential slab; driveways usually 5–6″.
Formula used: volume = L × W × depth (rect) or π × (d/2)² × depth (round), ÷ 27 for cubic yards. Bags = ceiling(volume ÷ bag yield). Ready-mix usually wins above ~1–2 yards.
Guides
FAQ
How many 80-lb bags of concrete are in a cubic yard?
About 45. Each 80-lb bag yields roughly 0.6 cubic feet, and a cubic yard is 27 cubic feet. For 60-lb bags (about 0.45 cu ft each), plan on about 60 per yard.
Should I order extra concrete?
Yes — 5–10% beyond the math. Forms flex outward, subgrades dip, and the cost of a second delivery or a cold joint dwarfs the price of a few spare bags.
When does ready-mix delivery beat bags?
Usually above 1–2 cubic yards. Mixing 90 bags by hand is a brutal day; a truck shows up and it's done in an hour. Compare both costs in the calculator above.
Tools for the job
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