Use this sonotube concrete calculator to find concrete volume, bags needed, and cost for sonotubes, round columns, and cylindrical footings.
Estimates only. By using this calculator you agree to our Terms.
| Measurement | Value | Unit | Result |
|---|
Enter the diameter and depth of your sonotube or round column, select your unit system (imperial or metric), and specify how many tubes you need to fill. Optionally enter your bag size and cost per bag to get a full materials estimate. Hit Calculate to instantly see cubic feet, cubic yards, number of bags required, and total material cost.
Ordering the right amount of concrete for sonotubes is one of those tasks that looks simple but bites you in the field. Too little and you're making an emergency trip to the hardware store mid-pour. Too much and you're paying for material you'll throw away — bagged concrete runs $7–$9 per 80 lb bag.
Consider a common scenario: building a deck with eight 12-inch diameter footings, each going 42 inches deep (below the frost line in colder climates). Each footing holds about 2.75 cubic feet of concrete, for a total of roughly 22.0 cubic feet across all eight. Once you round up to whole bags per footing and add a standard 10% waste allowance, that comes out to about 48 bags of 80 lb pre-mix — somewhere around $336–$432 depending on local pricing. Get the count wrong and you're either scrambling mid-pour for more bags or hauling home unused concrete. This calculator handles multiple columns at once and factors in a customizable waste percentage so you order the right amount the first time.
Beyond decks, this tool works for fence posts in large sonotubes, structural columns in additions, dock pilings, mailbox footings, lamp posts, pergola bases, and any other cylindrical concrete pour.
The volume of a cylinder (which is what a sonotube creates) uses the standard formula:
The result in cubic inches is converted to cubic feet (÷ 1,728) and then to cubic yards (÷ 27). Waste is added to the per-column volume first, then bags needed for one column = the waste-adjusted volume divided by the bag's yield, rounded up (you can't buy a fraction of a bag). That per-column bag count is then multiplied by the number of columns to get your total.
Say you're pouring a single 12-inch diameter sonotube, 48 inches deep, using 80 lb bags (0.6 ft³ yield each) with 10% waste:
So a single 12×48-inch tube needs about 3.14 cubic feet of concrete, which rounds up to 6 bags of 80 lb pre-mix. At $8 per bag, that's roughly $48 for one footing.
10-inch and 12-inch diameter tubes are by far the most common for residential decks. A 12×48-inch tube (4 feet deep) holds about 3.14 cubic feet of concrete — roughly 6 bags of 80 lb pre-mix once you account for standard waste. Larger decks or those carrying hot tubs often require 14-inch or 16-inch tubes.
Absolutely. Just use the cubic yards result. Ready-mix is typically ordered in quarter-yard increments with a minimum order of 1 yard. If your total is under 1 yard, bagged concrete is usually more economical since you'd pay for a full yard anyway.
A standard mix weighs approximately 4,050 lbs (about 2 tons) per cubic yard. An 80 lb bag yields roughly 0.6 cubic feet and there are 27 cubic feet in a yard, so you'd need about 45 bags to equal one cubic yard — confirming why ready-mix is economical for larger pours.
Footing depth is determined by your local frost line depth, which is set by your building department and varies by region — it is not related to plant hardiness zones. Depths commonly range from about 12 inches in warm southern climates to 42 inches or more in cold northern regions, so check with your local permit office for the exact requirement before you dig.
Both brands are widely available and perform comparably for residential footings. Quikrete 5000 and Sakrete High Strength both reach 5,000 PSI in 28 days, which is excellent for footings. For most deck footings, standard 4,000 PSI 80 lb bags are perfectly adequate and slightly cheaper.