Count the 20 kg bags you need.
⚙️Calculation Parameters
📊Calculated Output
How 20 kg Concrete Bag Calculator Works?
To count 20 kg bags, the 20 kg Concrete Bag Calculator divides the form volume by 0.009 cubic meters (m³), the yield of one 20 kg bag. The process takes 4 steps.
Enter metric dimensions
Type the diameter in centimeters (cm) and depth in meters (m) or cm.
Calculate m³
The calculator finds the fill in m³ and liters (L).
Divide by 0.009 m³
One 20 kg bag yields about 9 L (0.32 ft³) of placed concrete.
Read bags and weight
The tool rounds up and shows the bag count and the total kilograms (kg) to carry.
20 kg Concrete Bag Calculator Formula
The 20 kg Concrete Bag Calculator uses a 9 L yield.
Bag count
Bags = ⌈V (m³) ÷ 0.009⌉Or ⌈V (L) ÷ 9⌉.
Rise per bag
h (cm) = 9,000 ÷ (π × (D ÷ 2)²)D in cm; cm of form height 1 bag fills.
Bags per m³
1 ÷ 0.009 ≈ 111 bagsAbout 2,222 kg of dry mix per m³.
Worked example: 6 fence posts in 20 cm × 1.0 m forms
- V = 6 × 0.0314 = 0.1885 m³ (188 L)
- Bags = ⌈188 ÷ 9⌉ = 21 bags
- Weight = 420 kg (926 lb)
20 kg Concrete Bag Calculator Conversion Table
The 20 kg bag conversion table lists the form height 1 bag fills and bag counts at 1.0 m and 1.2 m (39 in and 47 in) depths.
| Form diameter | Height per bag | Bags at 1.0 m | Bags at 1.2 m | Bags at 1.2 m + 10% |
|---|---|---|---|---|
| 15 cm (5.9 in) | 50.9 cm | 2 | 3 | 3 |
| 20 cm (7.9 in) | 28.6 cm | 4 | 5 | 5 |
| 25 cm (9.8 in) | 18.3 cm | 6 | 7 | 8 |
| 30 cm (11.8 in) | 12.7 cm | 8 | 10 | 11 |
| 40 cm (15.7 in) | 7.2 cm | 14 | 17 | 19 |
| 45 cm (17.7 in) | 5.7 cm | 18 | 22 | 24 |
Yield is about 9 L per 20 kg bag. Check the product label.
What is 20 kg Concrete Bag Calculator?
A 20 kg Concrete Bag Calculator is a metric bag counter set to the 9 L (0.009 m³) yield of a 20 kg bag of premixed concrete.
The 20 kg bag is a common size in Australia, New Zealand, the United Kingdom (UK) and parts of Europe and Asia, often sold for post setting. The light weight suits one-person handling. A 20 cm form rises 28.6 cm per bag.
The calculator works entirely in metric, so no pound or cubic foot conversion is needed.
What are the uses of 20 kg Concrete Bag Calculator?
There are 4 main uses of the 20 kg Concrete Bag Calculator.
Post setting abroad
Installers count 20 kg bags for fence and pergola posts.
Light handling
Owners pick a bag one person can carry.
Small forms
Builders fill 15 cm to 25 cm round forms.
Metric shopping
Buyers match the bag count to the store shelf.
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