Concrete per foot of tube
| Diameter | ft³ per foot | 60 lb bags per foot | 80 lb bags per foot |
|---|---|---|---|
| 6 in | 0.20 | 0.44 | 0.33 |
| 8 in | 0.35 | 0.78 | 0.58 |
| 10 in | 0.55 | 1.21 | 0.91 |
| 12 in | 0.79 | 1.75 | 1.31 |
| 14 in | 1.07 | 2.38 | 1.78 |
| 16 in | 1.40 | 3.10 | 2.33 |
| 18 in | 1.77 | 3.93 | 2.95 |
| 24 in | 3.14 | 6.98 | 5.24 |
Sonoco’s spec sheet lists 0.20, 0.35, 0.55 and 0.80 ft³ per foot for its 6–12 in Builder’s Tube. The first three match the table; for 12 in, π × 0.5² is 0.785, which Sonoco rounds up to 0.80 and the table shows as 0.79.
The formula
Work in feet: a 12 in tube has a radius of 0.5 ft, so each foot of height holds π × 0.5² = 0.785 ft³.
Don’t forget what’s under the tube
Most piers stand on a wider footing or a bell-shaped base so the load spreads over more soil. That concrete isn’t in the tube, so add it separately — the footing calculator handles square pads, and bell forms list their volume on the packaging.
Questions people ask
How many bags for a 12 in Sonotube?
A 12 in tube holds 0.79 ft³ per foot, so a 4 ft tube holds 3.14 ft³: 7 bags of 60 lb mix (6.98) or 6 bags of 80 lb (5.24). Quikrete’s Quik-Tube sheet says 7 × 60 lb; Sonoco says 8, which builds in a margin.
How many bags for a 10 in or 8 in tube, 4 ft tall?
A 10 × 48 in tube is 2.18 ft³ — 5 bags of 60 lb or 4 of 80 lb. An 8 × 48 in tube is 1.40 ft³ — 4 bags of 60 lb or 3 of 80 lb.
What sizes do tube forms come in?
Sonoco’s Builder’s Tube comes in 6, 8, 10 and 12 in diameters; its heavier lines go much larger — the Commercial tube from 6 to 60 in. Quikrete’s Quik-Tube is sold in 8, 10 and 12 in, usually in 4 ft lengths.
How deep does a tube need to go?
Deep enough that its footing sits below the frost line and at least 12 in below undisturbed ground (IRC R403.1.4). Your plans and local code set the exact depth.
Sources for the numbers on this page
- Sonoco — Sonotube Builder’s Tube concrete forms — specification sheet · checked October 1, 2026
- Quikrete — Quik-Tube building form — data sheet · checked October 1, 2026
- Quikrete — Concrete Mix No. 1101 — technical data sheet (bag yields, strength gain, curing) · checked October 1, 2026
- National Ready Mixed Concrete Association — CIP 8 — Discrepancies in yield (ordering 4–10% extra) · checked October 1, 2026
Corrections and updates are logged on the sources page.