Sonotube Calculator
Estimate concrete volume, bags and optional material cost for cylindrical form footings.
Use this Sonotube calculator to estimate concrete for cylindrical deck, porch, shed and structural footings. Choose Imperial or Metric units, select a tube diameter and bag size, enter hole depth and footing quantity, then add waste to estimate cubic volume, bags and optional cost.
Your Estimate
Volume of One Footing
2.36 cu ft
Total Concrete Volume
9.42 cu ft
Waste-Adjusted Volume (10%)
10.37 cu ft
Cubic Feet
10.37 cu ft
Cubic Yards
0.38 cu yd
Cubic Meters
0.294 m³
Concrete Bags Required
18 bags
Uses an estimated yield of 0.600 cu ft per 80 lb bag. Bag yields vary by product; confirm the package label before purchasing.
Results Actions
Typical Cylindrical Footing Planning Sizes
These diameter ranges describe common planning applications, not structural recommendations. Required diameter, depth, reinforcement and bearing area depend on loads, soil, frost depth, approved plans and local code.
How to Use the Sonotube Calculator
- 1Choose Imperial or Metric units.
- 2Select the cylindrical form diameter.
- 3Enter hole depth in feet or meters and the number of identical footings.
- 4Choose a 5%, 10% or 15% waste allowance.
- 5Select a native pound or kilogram concrete bag size.
- 6Optionally enter the price per bag.
- 7Review one-footing volume, total volume, waste-adjusted volume, cubic-unit conversions, bags and optional cost.
Sonotube Cylinder and Bag Formulas
- 1Radius = selected tube diameter ÷ 2.
- 2Volume of one footing = π × radius² × hole depth.
- 3Total volume = one-footing volume × number of footings.
- 4Waste-adjusted volume = total volume × (1 + waste percentage).
- 5Cubic yards = cubic feet ÷ 27; one cubic meter equals about 35.3147 cubic feet.
- 6Bags required = waste-adjusted volume ÷ estimated yield per selected bag, rounded up.
- 7Estimated material cost = bags required × price per bag when a price is entered.
Example Calculation
Imperial example: four 12 in diameter footings, each 3 ft deep, contain about 2.36 cu ft each and 9.42 cu ft total. With 10% waste, the order volume is about 10.37 cu ft or 0.38 cu yd. At 0.60 cu ft per 80 lb bag, round up to 18 bags; at $7 per bag, estimated cost is $126. Metric example: four 300 mm footings at 0.9 m deep contain about 0.0636 m³ each and 0.254 m³ total. With 10% waste, the volume is about 0.280 m³. At 0.0135 m³ per 30 kg bag, round up to 21 bags.
Accuracy & Assumptions
- Results are planning estimates only and do not size structural footings.
- Each footing is modeled as a full, straight cylinder with a uniform diameter and depth.
- All footings entered together are assumed to be identical.
- Waste is applied after individual footing volumes are combined.
- Imperial bag yields assume approximately 0.0075 cu ft per pound of dry mix.
- Metric bag yields assume approximately 0.00045 m³ per kilogram of dry mix.
- Actual bag yield varies by manufacturer, mix design, water content and consolidation; use the package yield when available.
- Bell-shaped bases, over-excavation, voids, above-grade tube height and displaced volume from posts or reinforcement can change actual concrete needs.
- Footing diameter, depth, reinforcement, bearing area and frost protection must follow approved plans, soil conditions and local code.
Frequently Asked Questions
How do I calculate concrete for a Sonotube?
Treat the footing as a cylinder: multiply π by radius squared and depth, then multiply by the number of identical footings and add waste.
What Sonotube diameter should I use for a deck?
Diameter depends on tributary load, post spacing, soil bearing capacity, frost conditions and local code. Use the diameter shown on approved plans or provided by a qualified designer.
How deep should a cylindrical footing be?
Depth depends on frost depth, soil, uplift, structural loads and local requirements. Footings commonly need to extend below local frost depth, but the calculator does not determine required depth.
How many 80 lb bags fill a 12-inch Sonotube?
A 12 in diameter tube uses about 0.785 cu ft per foot of depth. An 80 lb bag yields roughly 0.60 cu ft, so bag count depends on total tube depth, quantity and waste.
Why does bag count round up?
Concrete bags are purchased as whole units. Rounding up reduces the chance of running short because of small measurement differences, spillage or yield variation.
Are metric bag yields exact conversions of U.S. bags?
No. Metric mode uses native kilogram bag options and approximate yields. Products vary by region and manufacturer, so confirm the yield printed on the bag.
Does this calculator include a flared or bell-shaped base?
No. It assumes a straight cylinder. Calculate additional base volume separately when plans require a bell, pad or enlarged footing.
Does rebar or a post reduce concrete volume?
The calculator does not subtract displaced volume for reinforcement or embedded posts. That displacement is usually small for planning, but follow project details for final quantities.
Is Sonotube a generic term?
Sonotube® is a registered brand of concrete forming products. This calculator is a general cylindrical concrete-form estimator and is not affiliated with or endorsed by the trademark owner.
This calculator provides a preliminary concrete quantity estimate for straight cylindrical forms only and does not design structural footings. Required diameter, depth, reinforcement, bearing area, concrete strength and frost protection depend on structural loads, approved plans, soil conditions and local code. Confirm footing requirements and product-specific bag yields before excavation or placement. Sonotube® is a registered trademark; BuildCalculatorsHQ is not affiliated with or endorsed by the trademark owner.