Concrete Calculator

For a standard patio or walkway, 4 inches is the norm. Residential driveways need 4 to 6 inches, and heavy-duty slabs such as RV pads or garage floors typically require 6 to 8 inches poured over a compacted gravel base. Enter your chosen thickness in the calculator to get an exact yardage figure.

One cubic yard equals 27 cubic feet. At 0.45 cuft per bag, a 60 lb mix takes 60 bags; at 0.6 cuft per bag, an 80 lb mix takes 45 bags. For pours above about 1 cubic yard, ready-mix truck delivery usually costs less than buying bags.

Standard cured concrete weighs about 150 lbs per cubic foot, which comes out to roughly 4,050 lbs (just over 2 tons) per cubic yard. Lightweight mixes run 90 to 115 lbs per cubic foot. The calculator reports volume only, not weight, so use these figures if you need to check load capacity.

Spillage, uneven subgrade, over-excavation, and form variation can increase the required concrete. The calculator shows base cubic yards, while its bag estimates include the selected waste allowance. Apply the waste factor to cubic yards separately before requesting a ready-mix quote.

The calculator handles round columns directly: select the Column shape, enter the diameter and height in feet, and it applies pi x (diameter / 2)^2 x height. For example, a 1 ft diameter column that is 8 ft tall needs 6.28 cubic feet (0.23 cubic yards). If you are working by hand, divide cubic feet by 27 to get cubic yards.