Slab size
Thickness units
Waste
Order
- Cubic yards
- —
- 60 lb bags
- —
- 80 lb bags
- —
Enter length, width, and thickness.
This is an estimate, not structural engineering, not a mix design, and not a price quote. It does not choose thickness, strength (PSI), or reinforcement. Confirm volume and mix with your ready-mix plant or inspector. Check the yield printed on the bag.
How the volume is counted
Slab volume is length × width × thickness. Thickness in inches is divided by 12 to get feet, then divided by 27 to get cubic yards. Waste is extra material — 10% is a common pad for spillage and uneven subgrade.
Bag counts always round up. Typical yields used here: 80 lb → 0.60 cubic feet, 60 lb → 0.45 cubic feet. The bag in your hand may differ.
Example: 10 ft × 10 ft × 4 in with 10% waste is 1.36 yd³ — 62 bags of 80 lb, or 82 bags of 60 lb.
FAQ
How much concrete for a 10×10 slab?
At 4 inches thick, 1.23 cubic yards before waste. With 10% waste: 1.36 yards, 62 bags of 80 lb. Enter your own thickness above.
How many 80 lb bags in a yard?
About 45, using 0.60 cubic feet per bag (27 ÷ 0.60). Round up for the leftover.
Bags or a truck?
Under about 1 cubic yard, bags are usually simpler. Over 1 yard, call a ready-mix plant. That is a rule of thumb, not a quote.