Enter slab dimensions and thickness to estimate concrete in cubic yards and bags. Add multiple slab sections, allowance and optional local pricing.
Your concrete estimate
Order approximately
—yd³
—Calculated geometric volume
—Recommended order quantity
—Bag equivalent · buy count rounded up
—Approximate order weight
Planning estimate only. Bag yield, density, supplier practices and project conditions vary. Confirm quantities with your supplier; this is not an engineering specification.
Measure the planned pour length and width, then enter the slab thickness in inches (or centimeters in Metric mode). For separate areas, add each non-overlapping section once. If thickness varies, enter sections separately so each depth is represented.
An uneven subgrade can change the placed quantity. This calculator multiplies the dimensions and thickness you enter; it does not assess the base or structural design. Confirm the quantity with your concrete supplier.
Worked slab example
A 12 × 20 ft slab at 4 inches thick has a geometric volume of 80 ft³, approximately 2.96 yd³. A user-selected 10% allowance—shown only as an illustration, not a universal recommendation—raises the estimate to 88 ft³, approximately 3.26 yd³. At the selected label yield of 0.60 ft³ per bag, that is 147 whole 80 lb bags.