Type the size in cm and m.
⚙️Calculation Parameters
📊Calculated Output
How Metric Sonotube Calculator Works?
To size a Sonotube in metric units, the Metric Sonotube Calculator accepts diameter in centimeters (cm) and depth in meters (m), then reports cubic meters (m³), liters (L) and metric bag counts. The process takes 4 steps.
Enter diameter in centimeters
Type the form diameter in cm. Metric suppliers sell round forms from 15 cm to 60 cm, with 20 cm, 25 cm and 30 cm the most common sizes for posts and decks.
Enter depth in meters
Type the pour depth in m. Frost depths in Canada and northern Europe run from 1.2 m to 1.8 m.
Read m³ and liters
The calculator returns the fill in m³ for ready-mix orders and in L for hand mixing.
Read metric bag counts
The tool divides the volume by 0.011 m³ for 25 kg bags and 0.009 m³ for 20 kg bags and rounds up.
Metric Sonotube Calculator Formula
The Metric Sonotube Calculator keeps every step in SI units, so no imperial conversion happens unless you ask for it.
Volume in m³
V = π × (D ÷ 200)² × HD in cm and H in m.
Liters
L = V × 1,0001 m³ = 1,000 L.
Metric bags
Bags = V ÷ bag yield (m³), rounded up25 kg ≈ 0.011 m³ and 20 kg ≈ 0.009 m³ of placed concrete.
Worked example: 25 cm × 1.2 m deck pier
- r = 25 ÷ 200 = 0.125 m
- V = 3.1416 × 0.125² × 1.2 = 0.0589 m³ (58.9 L)
- 25 kg bags = 0.0589 ÷ 0.011 = 5.35, so buy 6 bags
Metric Sonotube Calculator Conversion Table
The metric conversion table lists 8 metric form sizes with their inch equivalent, m³ per meter of depth and bag counts at a 1.2 m (47 in) depth.
| Diameter (cm) | Diameter (in) | m³ per 1 m | m³ at 1.2 m | 25 kg bags | 20 kg bags |
|---|---|---|---|---|---|
| 15 cm | 5.9 in | 0.0177 | 0.0212 | 2 | 3 |
| 20 cm | 7.9 in | 0.0314 | 0.0377 | 4 | 5 |
| 25 cm | 9.8 in | 0.0491 | 0.0589 | 6 | 7 |
| 30 cm | 11.8 in | 0.0707 | 0.0848 | 8 | 10 |
| 35 cm | 13.8 in | 0.0962 | 0.1155 | 11 | 13 |
| 40 cm | 15.7 in | 0.1257 | 0.1508 | 14 | 17 |
| 50 cm | 19.7 in | 0.1963 | 0.2356 | 22 | 27 |
| 60 cm | 23.6 in | 0.2827 | 0.3393 | 31 | 38 |
Bag yields vary by brand. Check the yield printed on the bag before ordering.
What is Metric Sonotube Calculator?
A Metric Sonotube Calculator is a concrete form calculator that takes diameter in centimeters and depth in meters and returns volume in cubic meters, liters and kilogram bag counts.
Imperial calculators force metric users to convert twice: once on the way in and once on the way out. The metric version removes both steps and rounding drift. A 30 cm × 1.5 m pier needs 0.106 m³, which equals 10 bags of 25 kg mix.
The calculator matches the units on metric drawings, metric tape measures and metric bag labels sold in Canada, the United Kingdom (UK), the European Union (EU), Australia and India.
What are the uses of Metric Sonotube Calculator?
There are 4 main uses of the Metric Sonotube Calculator.
Canadian deck permits
Builders match pier sizes on metric permit drawings to a concrete order.
European post bases
Installers size round bases for fences, carports and signs in cm and m.
Metric bag shopping
Buyers get a direct count of 20 kg or 25 kg bags.
Engineering checks
Designers verify pier volumes on SI structural schedules.
🔗Related Sonotube Calculators
View all 106 subtools →Imperial Sonotube Calculator
Type the size in feet and inches.
Mixed-Unit Sonotube Calculator
Mix feet, inches, cm and m in one job.
Sonotube Volume Calculator
Find how much concrete fills a round tube.
Sonotube Cubic Yards Calculator
See your concrete in cubic yards.