Concrete Calculator — Concrete Bags Calculator
The bags view starts from a volume instead of a shape: enter cubic feet (or compute them in any other view) and get whole-bag counts for 80, 60, and 40 lb pre-mixed concrete, rounded up and including the waste factor. Built for the small-pour decision — a 4 × 4 ft stoop pad at 4 inches is 5.33 cubic feet and needs just 10 80-lb bags, firmly in bag territory, while anything approaching the 45-bags-per-cubic-yard mark belongs on a ready-mix truck.
Concrete volume
Concrete to order
1.1 yd³
27 ft³ · 1 yd³ before waste · 50 × 80 lb bags
Breakdown
Volume = shape geometry × a disclosed waste factor; 1 cubic yard = 27 cubic feet. Bag counts use standard pre-mixed yields (80 lb ≈ 0.60 ft³). A planning estimate for ordering, not an engineering specification.
The bag math
Each bag size has a published yield (QUIKRETE product data, checked 2026-06-10): 0.60 cubic feet from an 80 lb bag, 0.45 from a 60 lb bag, 0.30 from a 40 lb bag. Divide the waste-adjusted volume by the yield and round up — partial bags can't be poured, so the calculator never rounds down. A full cubic yard works out to 45, 60, or 90 bags respectively.
Bigger bags mean fewer trips and a lower price per cubic foot; smaller bags are easier on the back and easier to mix completely in a wheelbarrow. The 4 × 4 ft pad example splits the difference visibly: 10 bags at 80 lb, 14 at 60 lb, or 20 at 40 lb for the same 5.86 waste-adjusted cubic feet.
When bags beat a truck — and when they stop
Bags win on small pours: no delivery minimum, no short-load fee, no schedule window, and the unused bags return to the store. Post footings, stoop pads, repair patches, and anything under roughly half a cubic yard are natural bag jobs.
The limit is labor and timing, not arithmetic. Sixty-two 80-lb bags — the 10 × 10 ft slab at 10% waste — is nearly 5,000 pounds to load, haul, and mix batch by batch while the earlier batches cure. Past the one-cubic-yard mark, a ready-mix delivery is usually cheaper per yard and produces one consistent, continuously placed mix instead of dozens of hand batches.
Questions
- How many cubic feet does an 80 lb bag of concrete yield?
- About 0.60 cubic feet per QUIKRETE product data; 60 lb bags yield about 0.45 and 40 lb bags about 0.30. Yields vary slightly with water content.
- How many bags of concrete are in a cubic yard?
- 45 80-lb bags, 60 60-lb bags, or 90 40-lb bags — a cubic yard is 27 cubic feet, divided by each bag's yield.
- How many bags do I need for a small pad?
- A 4 × 4 ft pad at 4 inches is 5.33 cubic feet; with 10% waste that is 10 80-lb bags, 14 60-lb bags, or 20 40-lb bags, rounded up to whole bags.