Sonotube / Column Footing Calculator

Calculate how many bags of concrete you need to fill round tube forms (sonotubes), column footings, and round piers. Add multiple tubes at once and get 60 lb, 80 lb, and ready-mix quantities.

Tube dimensions Multiple tubes
in
Must be below local frost depth
How many footings / columns
$
60 lb bag avg: $6–$9
Frequently asked questions
How deep should sonotube footings be? ›
Sonotube footings must extend below the local frost depth to prevent frost heave from lifting the posts and structure above. Frost depths vary from 0 inches in southern Florida to 60+ inches in northern Minnesota. Check your local building code or ask your building department for the required frost depth in your area. A good rule of thumb: add 6–12 inches below the frost line for a safety margin.
How many bags of concrete do I need for a 10-inch sonotube? ›
A 10-inch diameter tube at 48-inch depth has a volume of π × (5/12)² × 4 ft = 0.545 cu ft. A 60 lb bag fills 0.45 cu ft, so you need about 1.3 bags per tube — round up to 2 bags. For six 10-inch tubes at 48 inches, you need approximately 10 bags of 60 lb concrete. This calculator does the exact math for any diameter, depth, and quantity.
Should I use bags or ready-mix concrete for sonotubes? ›
For 1–8 tubes, bagged concrete is the most practical choice — no minimum order, no rush, and you can work at your own pace. For 10+ tubes or larger diameter tubes (14-inch and up), ready-mix concrete delivered by truck becomes more economical and faster. The break-even point is typically around 1 cubic yard (27 cu ft) — if your total volume is under 1 yard, use bags. Over 1 yard, get quotes from ready-mix suppliers.
Can I leave the sonotube form in the ground? ›
Above-grade portions of the sonotube should always be removed after the concrete cures (24–48 hours minimum) — cardboard tubes deteriorate and can wick moisture into the concrete and onto the post base. The below-grade portion can be left in place or removed — leaving it is common practice and generally acceptable. Some jurisdictions require removing the tube below grade to allow for soil contact and drainage; check local codes.

About this sonotube calculator

This calculator uses the cylinder volume formula (π × r² × h) to find the exact cubic feet of concrete needed per tube, multiplies by your tube count, adds the overfill factor, and divides by the yield of your chosen bag size to get the number of bags. It also shows the ready-mix volume in cubic yards for larger projects and generates a quick-reference table showing bags per tube for common sizes and depths.