Concrete & masonry calculators
Concrete Bag Calculator
You are at the home center staring at a pallet of 80-lb bags, doing mental math you do not trust. The bag says it yields 0.6 cubic feet, your slab is some number of cubic feet, and division under fluorescent lights is how people end up making three trips.
This calculator does the division honestly. Enter your volume directly, or enter slab dimensions and let it compute the volume first. Pick your bag size — 80, 60, or 50 lb — and it tells you exactly how many bags to buy, always rounded up, plus the total weight you will haul and what the same job would be as ready-mix. Bag yields come straight from the Quikrete spec sheet, and the formula is shown with your numbers below the results.
- Volume
- 48.0 cu ft
- Bags needed
- 80 bags80-lb bags, always rounded up — never round down concrete
- Total dry weight
- 6,400 lbabout 3.2 tons to haul
- As ready-mix
- 1.78 cubic yardsfor price comparison with a truck
How we calculate this (with your numbers)
Volume = 48.00 cu ft
Bags = 48.00 ÷ 0.6 cu ft per 80-lb bag = 80.0 → rounded up: 80 bags
Ready-mix equivalent = 48.00 ÷ 27 = 1.78 yd³
How the math works
Worked example
A 12 × 12 ft shed pad, 4 inches thick, using 80-lb bags:
- Volume = 12 × 12 × (4 ÷ 12) = 48 cu ft
- Bags = 48 ÷ 0.60 = 80 → 80 bags exactly
- Total dry weight = 80 × 80 = 6,400 lb (3.2 tons)
- Ready-mix equivalent = 48 ÷ 27 = 1.78 cubic yards
At 80 bags you are well past the point where a ready-mix truck is cheaper — see the break-even math in our Quikrete vs. ready-mix guide.
Limitations
Frequently asked questions
45 bags. Each 80-lb bag of Quikrete Concrete Mix #1101 yields about 0.60 cubic feet (per the product spec sheet), and a cubic yard is 27 cubic feet: 27 ÷ 0.60 = 45.
60 bags. The 60-lb bag yields about 0.45 cubic feet per the same spec sheet: 27 ÷ 0.45 = 60. For 50-lb bags (0.375 cu ft yield), it is 72 bags per yard.
Because running out mid-pour is the worst outcome in concrete work. Fresh concrete starts setting within about 90 minutes; a second batch mixed later creates a cold joint — a visible, weaker seam. One leftover bag costs a few dollars; a short pour can ruin a slab.
An 80-lb bag is 80 lb, obviously — but it adds up fast. Eighty bags (one cubic yard) is 6,400 lb, over 3 tons. Most half-ton pickups are rated for roughly 1,000–1,500 lb of payload, so a full yard of bagged concrete is multiple trips or a delivery. The calculator shows total dry weight so you can plan the haul.
Roughly above 1 cubic yard (45 eighty-pound bags). Bagged concrete runs about $4.50–$6.00 per 80-lb bag in 2026 (buildestimatory.com 2026 price guide), which works out to roughly $200+ per cubic yard in material alone — versus $125–$180 per yard delivered for ready-mix. Bags win on small jobs where short-load fees would punish a truck order.
Related calculators & guides
- Concrete calculator — cubic yards for slabs, with waste allowance
- Footing concrete calculator — volume for footings and posts
- Quikrete vs. ready-mix — full cost-per-yard comparison with bag tables
- How much does a yard of concrete cover?