Bag yield by product size
Published yields vary slightly by manufacturer and product line; these are common figures for standard pre-mixed concrete bags used for footings and posts.
| Bag size | Typical yield |
|---|---|
| 80 lb bag | ≈ 0.60 ft³ |
| 60 lb bag | ≈ 0.45 ft³ |
- Bag yields are manufacturer-published figures (commonly cited for QUIKRETE-type concrete mix) and can vary slightly by product — check the bag's technical data sheet for large orders.
- This calculator estimates concrete volume for the tube itself; it does not add extra volume for the base of the hole below the tube or for a wider footing spread, if applicable to the design.
What is a Sonotube footing, and how is its volume calculated?
A Sonotube (a generic term for a cylindrical cardboard concrete form) is commonly used to form round concrete footings or piers, such as deck post footings. Because the form is a cylinder, its volume follows the standard cylinder formula: the circular cross-sectional area multiplied by the tube's height.
Once the total volume is known, it can be converted into bag counts for pre-mixed concrete products using each product's published yield — the volume of finished concrete one bag produces once mixed with water.
How to use this Sonotube calculator
- Enter the tube diameter in inches (common Sonotube sizes range from 6 to 24 inches or more).
- Enter the tube height (the depth of the footing) in feet.
- Enter how many tubes are being filled.
- Read the total volume in cubic feet and cubic yards, plus the number of 80 lb or 60 lb bags needed.
The formula behind the Sonotube volume
Volume per tube equals π × (diameter ÷ 2)² × height, using the standard cylinder-volume formula. Total volume multiplies this by the number of tubes. Bag counts divide the total volume by each product's published yield — commonly about 0.60 cubic feet per 80 lb bag and about 0.45 cubic feet per 60 lb bag for QUIKRETE-type concrete mix.
Worked example: four tubes, each 12 inches (1 ft) in diameter and 8 ft tall, give a volume per tube of π × (0.5)² × 8 ≈ 6.28 ft³, for a total of 4 × 6.28 ≈ 25.13 ft³ (about 0.93 yd³). At 0.60 ft³ per 80 lb bag, that needs 25.13 ÷ 0.60 ≈ 41.9, rounded up to 42 bags.
Common mistakes
- Entering diameter when the manufacturer or supplier lists tube size by radius, or vice versa.
- Forgetting to convert tube height from inches to feet if measured that way.
- Not adding extra concrete for a below-grade footing base or bell shape that extends beyond the tube's cylindrical diameter.
- Ordering bags without a waste allowance for spillage during hand-mixing and placement.
Часто задаваемые вопросы
How much concrete do I need for a Sonotube footing?
Multiply π × (diameter ÷ 2)² by the tube height to get volume per tube, then multiply by the number of tubes — a 12-inch diameter, 8-foot-tall tube needs about 6.28 cubic feet.
How many 80 lb bags fill a 12-inch Sonotube 8 feet tall?
About 10.5 bags per tube (6.28 ft³ ÷ 0.60 ft³ per bag), so four such tubes need roughly 42 bags of 80 lb pre-mixed concrete.
What is the difference between 60 lb and 80 lb concrete bags?
They are the same basic pre-mixed concrete product at different package weights; an 80 lb bag yields about 0.60 cubic feet of concrete while a 60 lb bag yields about 0.45 cubic feet, so more 60 lb bags are needed for the same volume.
Do I need to add extra concrete for the footing base below the tube?
This calculator only computes the cylindrical tube volume; if the design includes a wider footing base or bell shape below the tube, add that volume separately.
Источники
- QUIKRETE technical data sheets — published concrete mix yield per bag (cubic feet per 60 lb / 80 lb bag).
- Sonoco / Sonotube manufacturer product literature — standard cylindrical concrete form sizes.
- American Concrete Institute (ACI) — general guidance on cylindrical footing and pier volume calculation.