Sonotube Concrete Calculator
Calculate concrete volume, bag count, and total weight for Sonotube cylinder forms. Handle multi-tube projects (decks, pergolas, pier foundations) in one calculation.
Results
Estimates only. Verify tube sizes on site, set tubes below your local frost line, and check building code for required diameter, depth, and rebar.
How to use this calculator
- 01Pick your tube diameter. The 6 standard sizes cover almost every residential pier; choose Custom for non-standard diameters and a numeric input appears below.
- 02Enter tube height in feet. Measure the full tube length — typically the depth below frost line plus any extension above grade.
- 03Set the Number of Tubes. This is the multi-tube part: enter 4, 6, 8, or however many piers your project uses, and the calculator returns the total pour in one go. Per-tube outputs appear when you have more than one tube.
- 04Choose your bag size and waste factor. 80-lb bags are most common for tube pours; 10% waste covers the partial-bag overage you cannot recover. For 4+ tubes totalling over 1 cubic yard, consider ready-mix delivery instead.
- 05Read the results. Total Concrete Needed includes waste and is the orderable cubic yardage. Total Bags is computed from total volume (not per-tube × tube count), so it can be slightly less than per-tube bags multiplied out — that is normal.
Understanding the math
A Sonotube is just a vertical cylinder. The volume of a cylinder is the area of the circular base times the height:
volume = π × radius² × height · radius = diameter / 2
The diameter input is in inches and the height in feet, so the calculator converts internally: with diameter in inches, the radius in feet is dIn / 24, and the per-tube volume in cubic feet simplifies to (π × dIn² × heightFt) / 576. Multiply by the number of tubes to get the project total.
For multi-tube projects, total bags is calculated from total volume directly — not by multiplying per-tube bags by tube count. That single rounding step gives the actual minimum bag demand. For example: 8 tubes at 12″ × 4 ft each round to 6 bags per tube individually (48 total if multiplied), but the project as a whole only needs 47 bags. The calculator returns 47 because that is the real demand.
Worked example: a single 12″ × 4 ft tube with 80-lb bags and 10% waste. Volume per tube = π × 144 × 4 / 576 = π = 3.14 cubic feet, or 0.116 cubic yards. With 10% waste: 0.128 cubic yards. Bags = π × 1.10 / 0.6 = 5.76, rounded up to 6 bags. Weight = 3.14 × 150 = 471 lbs.
Sonotube reference chart
Volume and 80-lb bag count for common Sonotube projects, computed at 10% waste. Use this to sanity-check the calculator output or to budget at a glance before measuring on site.
| Project | Tubes | Diameter | Height | Yards | 80-lb Bags |
|---|---|---|---|---|---|
| Mailbox post | 1 | 8″ | 3 ft | 0.04 | 2 |
| Deck pier (single) | 1 | 12″ | 4 ft | 0.12 | 6 |
| 4-pier deck | 4 | 12″ | 4 ft | 0.47 | 24 |
| 8-pier deck | 8 | 12″ | 4 ft | 0.93 | 47 |
| 6-pier pergola | 6 | 10″ | 3 ft | 0.36 | 18 |
| Heavy fence corner | 1 | 16″ | 4 ft | 0.21 | 11 |
| Commercial pier | 1 | 24″ | 6 ft | 0.70 | 35 |
Frequently asked questions
How much concrete do I need for a Sonotube?
Use the formula: π × radius² × height. For a 12" diameter (radius = 6") tube that's 4 feet deep: 3.14 × 0.5² × 4 = 3.14 cubic feet, or 0.116 cubic yards. Multiply by the number of tubes for total project volume. Add 5–10% waste because partial bags do not refill. The calculator above handles this automatically.
How many bags of concrete for a 12" Sonotube?
A 12" × 4-foot Sonotube needs about 3.14 cubic feet of concrete. Using 80-lb bags (which yield ~0.6 ft³ each), that is 6 bags per tube. For 60-lb bags it is 8 per tube; for 40-lb bags it is 11 per tube. For deck projects with multiple tubes, switching to ready-mix delivery becomes cheaper above ~1 cubic yard total.
What size Sonotube do I need for a deck?
Standard residential deck piers use 10-12" diameter Sonotubes set 3–4 feet deep (below frost line in cold climates). Heavier loads or larger decks may need 14-16" tubes. Check local building codes for required diameter and depth — frost line depth varies significantly by region. Always verify with your building inspector before pouring.
How deep should a Sonotube be?
Tubes must extend below the frost line for your area. Typical depths: northern climates 42-48 inches, mid-latitudes 30-36 inches, southern climates 12-24 inches. Check your local building code — frost depth is a code requirement, not optional. Above-frost installation will heave during freeze-thaw cycles and damage whatever sits on top.
Is it cheaper to use bags or ready-mix for Sonotubes?
For 1-3 tubes, bags are cheaper and more practical (you mix as you pour each tube). For 4+ tubes totaling more than ~1 cubic yard, ready-mix delivery wins on cost and time. Mixing bags by hand for a 6-pier deck means moving 30+ bags and managing wet concrete in batches — a delivery truck pours all tubes in 30 minutes.
Do I need rebar in a Sonotube?
For most residential deck piers and posts, vertical rebar (typically #4 or #5, 2-3 pieces per tube) is recommended for strength and code compliance. Embed the rebar in the concrete with proper coverage from tube walls. Heavy structural piers may require more rebar plus horizontal ties. Check your local code — requirements vary by load and soil conditions.
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Estimates only. Verify tube dimensions on site, set tubes below your local frost line, and check building code for required diameter, depth, and rebar. TakeoffCalc is not responsible for material over- or under-orders.