Sonotube Concrete Calculator
Concrete volume, bag count, and total weight for Sonotube cylinder forms. Multi-tube projects (decks, pergolas, pier foundations) handled in one calculation. For rectangular pier bases or strip footings, use the Concrete Footing Calculator.
Results
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 isn't responsible for material over- or under-orders.
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 (or meters in metric mode). 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 (36-kg) bags are most common for tube pours. 10% waste covers the partial-bag overage you can’t recover. For 4+ tubes totalling over 1 cubic yard (0.76 m³), 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’s normal.
Understanding the math
A Sonotube is 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 metric: same formula with diameter and height in meters, output in m³
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. In metric mode, the formula stays the textbook π × radius² × height with all inputs in meters. 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 (30 cm × 1.2 m) 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’s the real demand.
Worked example: a single 12″ × 4 ft (30 cm × 1.2 m) tube with 80-lb (36-kg) bags and 10% waste. Volume per tube = π × 144 × 4 / 576 = π = 3.14 cubic feet (0.089 m³), or 0.116 cubic yards (0.089 m³). With 10% waste: 0.128 cubic yards (0.098 m³). Bags = π × 1.10 / 0.6 = 5.76, rounded up to 6 bags. Weight = 3.14 × 150 = 471 lbs (214 kg).
Sonotube reference chart
Volume and 80-lb bag count for common Sonotube projects, computed at 10% waste. Useful for sanity-checking the calculator output or budgeting 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 | 0.13 | 6 |
| 4-pier deck | 4 | 12″ | 4 ft | 0.51 | 24 |
| 8-pier deck | 8 | 12″ | 4 ft | 1.02 | 47 |
| 6-pier pergola | 6 | 10″ | 3 ft | 0.40 | 18 |
| Heavy fence corner | 1 | 16″ | 4 ft | 0.23 | 11 |
| Commercial pier | 1 | 24″ | 6 ft | 0.77 | 35 |
Frequently asked questions
How to calculate concrete for a Sonotube?
Use the formula π × radius² × height. For a 12" (30 cm) diameter (radius = 6" / 15 cm) tube that's 4 feet (1.2 m) deep: 3.14 × 0.5² × 4 = 3.14 cubic feet (0.089 m³), or 0.116 cubic yards (0.089 m³). Multiply by the number of tubes for total project volume. Add 5-10% waste because partial bags don't refill. The calculator above does this automatically.
How many bags of concrete for a 12" Sonotube?
A 12" × 4-foot (30 cm × 1.2 m) Sonotube needs about 3.14 cubic feet (0.089 m³) of concrete. Using 80-lb bags (which yield ~0.6 ft³ each), that's 6 bags per tube. For 60-lb bags it's 8 per tube. For 40-lb bags it's 11 per tube. In metric, a 40 kg bag yields ~0.0188 m³, so the same tube needs about 5 bags. For deck projects with multiple tubes, ready-mix delivery becomes cheaper above ~1 cubic yard (0.76 m³) total.
What size Sonotube do I need for a deck?
Standard residential deck piers use 10-12" (25-30 cm) diameter Sonotubes set 3-4 feet (0.9-1.2 m) deep (below frost line in cold climates). Heavier loads or larger decks may need 14-16" (35-40 cm) tubes. Check local building codes for required diameter and depth. Frost line depth varies significantly by region. Verify with your building inspector before pouring.
How deep should a Sonotube be?
Sonotube depth is usually set by frost depth, soil conditions, and the load above the pier. Typical residential depths vary widely by region, so use the depth shown on your plans or required by local code before pouring.
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 (0.76 m³), 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?
Many structural piers use vertical reinforcement, but exact bar size, count, cover, and tie details depend on the load, soil, frost depth, local code, and project plans. Decorative or light-duty posts may have different requirements. Check local code or a qualified professional before pouring.
Can I use this calculator with metric measurements?
Yes. Switch the unit selector to Metric and the inputs, bag options, results, reference values, and examples update to metric units where applicable.
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