Sonotube Concrete Calculator
Using sonotubes? Calculate exactly how much concrete you need with our free tool. Get accurate estimates for any tube size.
Dimensions
Pro Tips
- →Sonotubes come in standard diameters: 8, 10, 12, 14, 16, 18, 24 inches
- →Buy tubes 6-12 inches longer than needed for cutting
- →Place tubes on gravel base for drainage
- →Backfill around tubes before pouring for stability
- →Remove cardboard tube after concrete sets (or leave in ground)
Includes 10% waste factor
Cost Estimate
Estimated material costs for your project
Recommendation: Bagged Concrete
For smaller projects, bagged concrete gives you more control and less waste.
26 bags × 80lb
0.58 cubic yards + delivery
Prices vary by location and time. Contact local suppliers for accurate quotes.
FREE POUR DAY CHEAT SHEET
Multiple Tubes. One Shot to Get Them Right.Multiple Tubes. One Shot to Get Them Right.
Built around your specific tube diameter, depth, and quantity — not a generic PDF. Free, in your inbox in 30 seconds.
- →Multi-tube fill sequenceThe right fill sequence when pouring multiple tubes from one mix
- →Anchor bolt timingAnchor bolt and hardware placement — timed before the window closes
- →Void-free consolidationConsolidation technique for each tube to eliminate voids
- →Tube-by-tube pour orderA tube-by-tube pour order that keeps mix workable across the whole job
- →Curing schedule with load date28-day curing schedule with the exact date your footings can take load
- →Tools & materials checklistTools and materials checklist sized to your tube count and depth
That's typically a professional pour. See costs ↓
For general step-by-step instructions, read our complete How To Calculate Concrete and How Many Bags.
Sonotube Sizes and Applications
Sonotubes are cardboard concrete form tubes manufactured in standard diameters. Choosing the right diameter depends on the load the footing will carry.
| Diameter | Common Use | Typical Depth |
|---|---|---|
| 8 in | Fence posts, light mailbox posts | 30–36 in |
| 10 in | Light deck posts (single-story, short spans) | 36–42 in |
| 12 in | Standard deck footings, pergola posts | 42–48 in |
| 14–16 in | Heavy deck footings, multi-story loads | 48–60 in |
| 18–24 in | Structural columns, heavy commercial loads | 60 in+ |
When in doubt, size up. A 12-inch tube costs roughly $8–15 more in concrete than a 10-inch tube — minimal compared to the cost of failure.
How Deep to Set Sonotubes
Depth depends on two factors: frost line depth and footing load. The footing must extend below the frost line to prevent heaving from freeze-thaw cycles.
Frost line depths by region (approximate):
| Region | Frost Line Depth |
|---|---|
| Deep South (FL, GA, AL, LA) | 0–6 in |
| Mid-Atlantic, Pacific Coast | 12–24 in |
| Midwest, Upper South | 30–48 in |
| Northern states (MN, WI, ME) | 48–60 in |
| Mountain states | 36–72 in (varies by elevation) |
Always check your local building code for the required frost line depth. Many jurisdictions require footings to extend below the frost line — not just to it.
Rule of thumb for deck footings: Depth should be at least 1/3 of the above-ground post height, with a minimum of 36 inches (or your local frost line depth, whichever is greater).
Concrete Quantity Reference: Bags per Sonotube
This table shows 80-lb bags needed per tube, including 10% waste, at common sizes. Use the calculator above for your exact configuration.
| Diameter | Depth: 36 in | Depth: 48 in | Depth: 60 in |
|---|---|---|---|
| 8 in | 2 bags | 2–3 bags | 3 bags |
| 10 in | 3 bags | 4 bags | 5 bags |
| 12 in | 4–5 bags | 6 bags | 7–8 bags |
| 16 in | 8 bags | 11 bags | 13 bags |
For 6 or more tubes at larger diameters, ready-mix delivery may be more cost-effective than bagged concrete. At 12 bags per 80-lb bag order, ready-mix becomes competitive on both price and time.
Pouring Sonotubes: Key Steps
- Excavate and set the tube. Dig the hole 6 inches wider than the tube diameter for backfilling. Set the tube on a 4–6 inch gravel base for drainage.
- Backfill and brace before pouring. Pack soil around the tube while checking plumb with a level. Diagonal lumber braces staked to the ground hold above-ground portions vertical.
- Pour in lifts. For tubes deeper than 36 inches, pour in 12-inch lifts and rod or vibrate each lift to prevent voids. A steel rod or length of rebar works for rodding.
- Set post hardware before concrete stiffens. If using post bases or anchor bolts, set them immediately after pouring while the concrete is still workable. Check alignment before it stiffens.
- Remove or score the tube. For above-grade sections, peel the cardboard after 24–48 hours. For below-grade, leave it — it will decompose.
For the full pouring process, see our how to pour concrete guide.