Take out the hole in a hollow column.
⚙️Calculation Parameters
📊Calculated Output
How Hollow Column Concrete Calculator Works?
To size a hollow column, the Hollow Column Concrete Calculator finds the outer cylinder and subtracts the inner void. The process takes 4 steps.
Enter the outer form
Type the outer tube diameter and the column height.
Enter the inner void
Type the diameter of the inner tube, pipe or core, and its length, if shorter than the column.
Subtract
The calculator subtracts the void from the outer volume.
Read the ring volume
The tool shows concrete in cubic feet (ft³), cubic yards (yd³) and bags, plus wall thickness.
Hollow Column Concrete Calculator Formula
The Hollow Column Concrete Calculator uses the annulus formula.
Ring volume
V = π × ((D_o ÷ 24)² − (D_i ÷ 24)²) × (H ÷ 12)D_o outer and D_i inner diameter.
Wall thickness
w = (D_o − D_i) ÷ 2Concrete thickness around the void.
Void share
S = (D_i ÷ D_o)² × 100%Percent of the column left hollow.
Worked example: 16 in outer form, 8 in inner pipe, 48 in tall
- V_outer = 5.585 ft³; V_inner = 1.396 ft³
- V = 4.189 ft³ (0.155 yd³)
- Wall = (16 − 8) ÷ 2 = 4 in; void share = 25%
Hollow Column Concrete Calculator Conversion Table
The hollow column conversion table compares 6 outer and inner diameter pairs at 48 in (122 cm) tall.
| Outer dia. | Inner dia. | Outer ft³ | Void ft³ | Concrete ft³ | Void share |
|---|---|---|---|---|---|
| 12 in | 4 in | 3.14 | 0.35 | 2.79 | 11% |
| 12 in | 6 in | 3.14 | 0.79 | 2.36 | 25% |
| 16 in | 6 in | 5.59 | 0.79 | 4.80 | 14% |
| 16 in | 8 in | 5.59 | 1.40 | 4.19 | 25% |
| 18 in | 8 in | 7.07 | 1.40 | 5.67 | 20% |
| 24 in | 12 in | 12.57 | 3.14 | 9.42 | 25% |
Keep at least 2 in (5 cm) of concrete wall, or the minimum in the design, around any void.
What is Hollow Column Concrete Calculator?
A Hollow Column Concrete Calculator is a concrete calculator that subtracts an internal cylindrical void, such as a pipe or inner tube, from a round column.
Hollow columns appear in 3 forms: a column cast around a drain or utility pipe, a decorative column cast around a removable inner tube, and a pier cast around a steel pipe post. The calculator keeps the void out of the concrete count.
A void half the outer diameter removes 25% of the volume. Ordering for a solid column wastes that concrete.
What are the uses of Hollow Column Concrete Calculator?
There are 4 main uses of the Hollow Column Concrete Calculator.
Utility chases
Builders cast columns around pipes and conduit.
Steel pipe posts
Crews fill the ring between a pipe post and an outer form.
Decorative columns
Designers cast light hollow columns.
Accurate orders
Estimators remove void volume from the order.
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