How the math works
A column is a cylinder. Volume is π × r² × height, where r is half the inside diameter. Sonotubes are sold by inside diameter in inches, so we convert diameter and height to feet before multiplying, then multiply by the number of identical columns you’re pouring at the same time. Divide by 27 to convert to cubic yards.
The waste factor (default 10%) covers pump-line prime and spillage — important for column pours because the tube can’t be topped off cleanly if you come up short.
When to order ready-mix vs. bags
A single 4-foot sonotube is almost always a bag job — a 10-inch tube at 4 feet is under a tenth of a yard. Once you’re pouring a deck full of six or more posts, or piers for a small addition, the total yardage often crosses the short-load threshold and ready-mix wins, especially if you can pour them all in one visit.
Column pours favor consistency — every tube gets the same mix at the same slump. That’s hard to do by hand across a dozen bags.
Getting a real quote
Defaults here are national ballparks. Call a local producer for firm pricing once you have your yardage — many small pours qualify for a reduced short-load fee if you can be flexible on delivery time.