Ordering too little concrete wastes time; ordering too much wastes money. This calculator tells you exactly how many bags of pre-mix or cubic yards of ready-mix concrete you need for any slab, patio, or foundation.
80-lb Bags Needed:
60-lb Bags Needed:
How to Use This Tool
Enter the length and width of the area in feet.
Enter the desired thickness in inches (standard driveway = 4 inches, sidewalk = 4 inches, patio = 4-6 inches).
Keep the waste factor at 10% or increase for irregular shapes.
Click Calculate to get bag count and cubic yards.
The Formula
Volume = Length x Width x Thickness. Each 80-lb bag yields approximately 0.60 cubic feet of concrete. Each 60-lb bag yields approximately 0.45 cubic feet. Ready-mix is sold by the cubic yard (1 yd = 27 ft^3).
Why It Matters
You are pouring a 20x10ft driveway at 4 inches thick. You need 2.47 cubic yards of concrete — about 38 bags of 80lb mix. Ordering 40 bags gives you a safety margin. Total cost: ~$240 at $6/bag.