Waste is not the slab
Uneven subgrade, spillage, and over-excavation eat extra concrete. The typical bag count includes a waste factor; the low/high range is there because that factor is a judgment, not a measurement.
Your numbers
How much concrete for this slab?
Length, width, and thickness. You get the volume and a bag count. Waste is listed separately.ft
ft
in
Waste, bag size and price
Defaults cover a typical pour. Change them to match your supplier.
%10% is a planning default you can change
$
Plan to buy
62 × 80 lb bagsTypical range: 56 to 64 bagsMeasured volume1.235 yd³Before waste
Planning volume1.358 yd³Includes 10%
Material costAdd a bag priceBags only, not delivery
How we got this
- Measured volume10 ft × 10 ft × 4 in1.235 yd³
- Planning volumeIncludes your 10% allowance1.358 yd³
- 80 lb bags0.6 ft³ approximate yield per bag62 bags
What we assumed
- The shape is a rectangular slab with even thickness.
- Bag yields are approximate. Check the bag you buy.
- The range goes from measured volume to a little more than your waste percent.
- This is a quantity estimate, not structural advice.
Technical details
Method material-volume-v1.1.0Data quikrete-packaged-concrete-yields-2026-09
Discrepancy in the numbers? You can click Report incorrect result below or email hello@costanswer.com with the Method and Data lines.
Guide
Slab volume, bags, and waste
Length × width × thickness becomes cubic yards. Bag counts use published yield for the bag weight you pick. Waste is listed separately so the measured volume stays honest.
Questions about this calculator
How many 80 lb bags for a 10×10 slab?
It depends on thickness. A 4-inch slab is a different volume than a 6-inch slab. Type all three dimensions. The page will not assume 4 inches for you.
Is this ready-mix yards or bag count?
Both. Volume is cubic yards for a rectangular pour; bag count uses the packaged yield for the bag weight you pick, with waste called out separately.
Terms used here
- Cubic yard
- 27 cubic feet. Ready-mix is usually ordered in cubic yards.
- Yield
- How much volume a bag is rated to produce. The snapshot cites the packaged-concrete figures in use.
Practical tips
Order ready-mix in yards for anything larger than a small pad; bag math is for small jobs.
Confirm thickness. A patio and a driveway are not the same slab.
Limits and caveats
Volume math is exact for a rectangle. Bags and waste are planning estimates. Not an engineering spec.
Results are for information. They are not legal, tax, medical, or financial advice. How the math is maintained · Report a wrong figure.
Engine notes
Rounding, versioning, and omissions that sit beside the guide rather than repeating it.
- Thickness in feet. You enter inches. We convert to feet, then multiply by length and width to get cubic feet.
- Measured volume and a buy range. Your waste percent sets a typical bag count, with a higher bound five points above it.
- Bag yields. About 0.45 cubic feet for a 60 lb bag and 0.60 for an 80 lb bag. The count rounds up.