Pouring a slab, footing, or pad? This concrete calculator estimates how much concrete you need in cubic yards, plus an approximate number of pre-mixed bags — so you don’t order too little or waste money on extra.
How to Use This Calculator
Enter the length and width of the area in feet, and the slab thickness in inches. Click Calculate to see the volume in cubic yards and an estimated bag count.
Formula
Cubic feet = Length × Width × (Thickness ÷ 12). Cubic yards = Cubic feet ÷ 27. Bag estimate assumes a standard 60 lb bag yields about 0.45 cubic feet of mixed concrete.
This calculator gives a planning estimate only. For structural pours, confirm your quantities and mix design with a licensed contractor or engineer.
Frequently Asked Questions
How much concrete do I need for a 10×10 slab at 4 inches?
A 10×10 ft slab at 4 inches thick needs about 1.23 cubic yards, or roughly 74 bags of 60 lb mix.
Should I order extra concrete?
Yes — most contractors add 5-10% extra to account for spillage, uneven subgrade, and form imperfections.
Are 80 lb bags different from 60 lb bags?
An 80 lb bag yields about 0.6 cubic feet — divide your cubic feet total by 0.6 instead of 0.45 if using 80 lb bags.