CROCODILIAN
Concrete calculator

Concrete calculator — cubic yards

Slab dimensions to cubic yards and bags. Bag counts use the manufacturer's published yields, not guesses.

Area shape
ft
ft
in
$

Pre-filled example: a 10 × 10 ft slab at 4 inches. Bag yields from the Quikrete Concrete Mix data sheet; other brands differ slightly — check the bag.

Area
100 ft²
Volume
33.3 ft³
You need
1.23cubic yards
Order (rounded up)1.25 yd³
80 lb bags56
60 lb bags75
40 lb bags112
Estimates for planning — confirm quantities with your supplier.
Real-world quantities vary with moisture, compaction, cuts, and site conditions. These calculators use standard formulas and published constants (see the About page for sources); order with a sensible allowance and confirm with your supplier or contractor.

Bags or ready-mix?

The arithmetic makes the decision for you. One cubic yard is 45 bags at 80 lb — 3,600 pounds to haul, mix, and place before any of it starts setting. Bags shine for post holes, small pads, and repairs; for a slab of a yard or more, price a ready-mix delivery and spare your back. Whatever you choose, concrete is unforgiving of shortfalls — running out mid-pour creates a cold joint.

Per the manufacturer’s data sheet, standard concrete mix is for pours 2 inches thick or more, and placed concrete runs about 140 lb per cubic foot. Slab thickness, reinforcement, and base prep for your use case are structural questions — local code and professionals outrank any calculator.

Bag yields (manufacturer data)

Quikrete Concrete Mix bag yields — TDS No. 1101
Bag sizeYield per bagBags per ft³Bags per yd³
40 lb0.30 ft³3.3390
60 lb0.45 ft³2.2260
80 lb0.60 ft³1.6745

Yields from the Quikrete Concrete Mix technical data sheet (Oct 2022 revision). Other brands publish slightly different yields — the number on your bag wins.

Frequently asked questions