See how much tube one bag will fill.
⚙️Calculation Parameters
📊Calculated Output
How Tubes per Concrete Bag Calculator Works?
To count tubes per bag, the Tubes per Concrete Bag Calculator divides one bag yield by the volume of one small tube. The process takes 4 steps.
Enter a small tube size
Type the diameter and height of a shallow form, such as a 6 in × 12 in post sleeve.
Choose the bag
Select 40 lb, 60 lb or 80 lb, or enter a custom yield.
Divide bag by tube
The calculator divides the bag yield in cubic feet (ft³) by the tube volume.
Read tubes per bag
The tool shows decimal tubes per bag and whole tubes, plus the bags for your full count.
Tubes per Concrete Bag Calculator Formula
The Tubes per Concrete Bag Calculator inverts the usual bag count.
Tubes per bag
T = Y ÷ V_tubeY is bag yield and V_tube is one tube.
Whole tubes
T_whole = ⌊T⌋Complete tubes from 1 bag.
Bags for n tubes
Bags = ⌈n ÷ T⌉Bag count for a full set.
Worked example: 6 in × 12 in deck block forms with 80 lb bags
- V_tube = 0.1963 ft³
- T = 0.60 ÷ 0.1963 = 3.06 tubes per bag
- 20 forms need ⌈20 ÷ 3.06⌉ = 7 bags
Tubes per Concrete Bag Calculator Conversion Table
The tubes per bag conversion table lists how many shallow tubes 1 bag of 40 lb, 60 lb or 80 lb mix fills.
| Tube | ft³ per tube | Per 40 lb bag | Per 60 lb bag | Per 80 lb bag |
|---|---|---|---|---|
| 4 in × 12 in | 0.087 | 3.44 | 5.16 | 6.88 |
| 6 in × 12 in | 0.196 | 1.53 | 2.29 | 3.06 |
| 6 in × 18 in | 0.295 | 1.02 | 1.53 | 2.04 |
| 8 in × 12 in | 0.349 | 0.86 | 1.29 | 1.72 |
| 8 in × 18 in | 0.524 | 0.57 | 0.86 | 1.15 |
| 10 in × 12 in | 0.545 | 0.55 | 0.83 | 1.10 |
Values above 1.00 mean 1 bag fills more than 1 tube.
What is Tubes per Concrete Bag Calculator?
A Tubes per Concrete Bag Calculator is a small-form tool that shows how many shallow tubes one bag of concrete fills.
For tall piers, the question is bags per tube. For short forms, the question flips. A 6 in × 12 in form holds 0.196 ft³, so one 80 lb bag fills 3.06 of them. The calculator answers in that direction, which suits jobs with many small forms.
The tool helps with garden borders, shallow post sleeves, deck blocks and test samples.
What are the uses of Tubes per Concrete Bag Calculator?
There are 4 main uses of the Tubes per Concrete Bag Calculator.
Deck blocks
Builders cast many short 6 in to 8 in blocks from few bags.
Post sleeves
Installers fill shallow sleeves for removable posts.
Garden edging
Owners cast short round pavers and bollards.
Batch splitting
Crews split one mixed bag across several forms.
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