Concrete Footing Calculator

Footings are specified in inches and counted either in pads or in runs, which is how this page takes them. Give it a pad size and how many of them, or the total linear feet of a strip footing with its width and depth, and it returns the concrete in cubic yards, cubic feet and 60 and 80 lb bags, together with the reinforcing steel: bar lengths after cover is taken off, total linear feet, the weight at the ASTM nominal figure for that bar size, and how many twenty foot lengths that comes to. The site's concrete calculator will do a plain rectangle on its own, so what is here as well is the pad count, the lap and transverse bar allowances, and the steel. It counts material rather than sizing anything, so the width, the depth, the bar size and the spacing still come from the drawings and the local code.

Calculator Type
Units
Bar sizes stay the ASTM #3 to #8 and bar still comes in 20 ft lengths, because that is what is on the drawings and in the rack.
Footing trenches over-dig, so ten percent is a fair starting figure and more on soft ground.
A pad is usually reinforced with a mat: this many bars running one way and the same number running the other.
Three inches is the usual figure where concrete is cast against the ground. Your drawings decide it.
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Units
Bar sizes stay the ASTM #3 to #8 and bar still comes in 20 ft lengths, because that is what is on the drawings and in the rack.
Linear feet, or linear metres when Metric is selected. Add up every run. For a closed rectangle this is the perimeter along the centreline of the footing.
Footing trenches over-dig, so ten percent is a fair starting figure and more on soft ground.
Bars running the length of the footing. Two is common on a residential strip footing.
Bars overlap where they join and at corners. Ten percent covers an ordinary run; your drawings give the real lap length.
Inches between the bars, centre to centre.
Three inches is the usual figure where concrete is cast against the ground. Your drawings decide it.
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