AstraCalculator

Concrete Footing Calculator

For a strip footing under a wall, a garage or a deck. Enter the trench width, the thickness and how far it runs in total.

Add up every side. A 20 x 10 foot garage is 60 feet of footing.

Eight inches is common. Codes often want the footing at least as thick as it is wide beyond the wall.

Concrete poured straight against soil spreads into every soft spot in the trench wall.

How the math works

Volume = total run x width x thickness, all in feet, then multiplied by the waste allowance. A 16 inch wide footing is 1.333 feet wide. Divide the result by 27 for cubic yards.

Common questions

How wide should a footing be?
Twice the width of the wall it carries is the common rule of thumb, so a 8 inch block wall usually sits on a 16 inch footing. Your local code and your soil decide the real answer, and both are worth checking before you dig.
How deep does a footing have to go?
Below the frost line for your area, which is a few inches in the south and four feet or more in the north. A footing above frost depth will lift and crack the wall on it.
Can I pour a footing in sections?
Better not to. A footing works as one continuous beam, and a cold joint is a hinge. If it must be stopped, use a bulkhead and dowel across the joint.
Do I need rebar in a footing?
Most codes want two continuous bars near the bottom, lapped at the corners. It costs little and it is what holds the footing together when one end settles more than the other.

People also work out