Concrete for an 8-inch Sonotube
An 8-inch round tube holds 0.349 ft³ of concrete per foot of depth. A 4 ft tube takes 3 bags of 80-lb mix or 4 bags of 60-lb mix, with 10% extra.
- Per foot of tube0.349 ft³
- 4 ft tube1.40 ft³
- 80-lb bags (4 ft, +10%)3
- 60-lb bags (4 ft, +10%)4
Concrete needed
1.54 cubic feet
0.057 yd³ · 0.043 m³ · includes 10% extra
You need about 1.54 cubic feet of concrete, or 3 bags of 80 lb mix.
Bags of premix
- 640 lb bags
- 550 lb bags
- 460 lb bags
- 380 lb bags
- —20 kg bags
- —25 kg bags
- Before extra0.05 yd³ (1.4 ft³)
- Weight of bags240 lb
- Per hole—
- Ready-mix costAdd a price per yd³
- Bagged costAdd a price per bag
One 80 lb bag makes about 0.60 ft³ (manufacturer's published yield). Bags are rounded up.
Bagged mix makes sense at 0.06 yd³. A ready-mix truck for a load this small would usually come with a minimum-order or short-load charge.
Estimate only, not a quote or engineering advice. Disclaimer
An 8-inch tube is a common size for deck piers under a low, light deck, posts for a pergola, and similar small loads.
Bags per 8-inch tube by depth
| Depth | ft³ exact | 80-lb bags | 60-lb bags | 50-lb bags |
|---|---|---|---|---|
| 2 ft | 0.70 | 2 | 2 | 3 |
| 3 ft | 1.05 | 2 | 3 | 4 |
| 4 ft | 1.40 | 3 | 4 | 5 |
| 5 ft | 1.75 | 4 | 5 | 6 |
| 6 ft | 2.09 | 4 | 6 | 7 |
The math
For several tubes, set the number of columns in the calculator: it totals the volume before rounding, which can save a bag or two over multiplying the per-tube count. If the tube sits on a wider footing pad, add that as a separate footing.
Planning all the piers of a deck? Measure each tube's depth: when the ground slopes, the tubes on the low side are taller and need more concrete.
Frequently asked questions
How many bags of concrete for an 8-inch Sonotube?
Each foot of a 8-inch tube holds 0.349 ft³. A 4 ft tube takes 1.40 ft³: 3 bags of 80-lb or 4 bags of 60-lb mix, including 10% extra.
How many cubic feet in an 8-inch Sonotube?
0.349 cubic feet per foot of length. Multiply by the depth in feet.
How much concrete for an 8-inch Sonotube 3 feet deep?
1.05 ft³, which is 2 bags of 80-lb or 3 bags of 60-lb mix with 10% extra.
Other tube sizes
Related
Sources
- QUIKRETE: Concrete Mix No. 1101 data sheet (Revised Oct 2022; checked Nov 11, 2026)