Concrete Calculator
Calculate how much concrete you need in cubic yards and standard bags for any slab, footing, or column.
Concrete needed
1.23 yd³
Cubic feet
33.3 ft³
40 lb bags
112
60 lb bags
75
80 lb bags
56
Estimates use standard pre-mixed bag yields (0.30 ft³ per 40 lb bag, 0.45 ft³ per 60 lb bag, 0.60 ft³ per 80 lb bag). Add 5–10% extra material for waste and uneven subgrade on real pours.
How the Concrete Calculator works
Choose whether you're pouring a slab or footing (using length, width, and thickness) or a round column (using diameter and height), enter your measurements, and the calculator finds the total volume needed in cubic feet and cubic yards.
It also converts that volume into an estimated number of standard 40 lb, 60 lb, and 80 lb premixed concrete bags, so you know roughly how much to buy either way.
Frequently asked questions
How much extra concrete should I order?
Most contractors add 5–10% extra to the calculated volume to account for waste, spillage, an uneven subgrade, and minor form imperfections — especially important for ready-mix deliveries, since you can't easily order a small top-up mid-pour.
How is the number of bags calculated?
Each bag size yields a specific volume of mixed concrete once combined with water — roughly 0.30 cubic feet for a 40 lb bag, 0.45 cubic feet for a 60 lb bag, and 0.60 cubic feet for an 80 lb bag. The calculator divides your total volume by each yield to estimate how many bags you'd need.
When should I order ready-mix instead of using bags?
As a rough guide, once a project needs more than around 1 cubic yard of concrete, ready-mix delivery is usually more practical and often cheaper than buying and mixing dozens of bags by hand.