Sonotube / Concrete Column Calculator

This page opens the concrete calculator set up for a round column pour — a sonotube form for a deck footing, a fence post footing, or a freestanding concrete pier. Enter the tube's diameter in inches or centimeters (common sonotube sizes run 8, 10, 12, 18 and 24 inches) and its height in feet or meters; the calculator applies the cylinder formula π × radius² × height.

Diameter matters more than most people expect because it's squared in the formula: doubling a tube's diameter quadruples its volume for the same height. A 12-inch-diameter, 4-foot-tall column holds about 3.14 ft³ (roughly 0.12 yd³); step up to an 18-inch tube at the same height and it jumps to about 7.07 ft³ — more than double, from a 50% wider tube.

Deck footings and fence posts commonly need multiple identical columns — if that's your job, this tool's post-holes shape totals several holes in one pass instead of multiplying a single column's result by hand. Whichever you use, tick the waste checkbox for a 10% margin, since sonotube forms are rarely perfectly round or perfectly full to the brim. Everything is calculated locally in your browser.