Get the volume of a bell base you set.
⚙️Calculation Parameters
📊Calculated Output
How Bell Footing Volume Calculator Works?
To size a bell footing, the Bell Footing Volume Calculator treats the flared base as a frustum (a cone with the tip cut off) and adds the straight tube above it. The process takes 4 steps.
Enter the bell geometry
Type the bottom diameter of the bell and its height from the base to where it meets the tube.
Enter the tube
Type the tube diameter and the tube height above the bell.
Calculate the frustum
The tool applies the frustum formula with the tube diameter as the top and the bell diameter as the bottom.
Total the pier
The calculator adds bell and tube volumes in cubic feet (ft³) and bags.
Bell Footing Volume Calculator Formula
The Bell Footing Volume Calculator combines a frustum and a cylinder.
Bell (frustum)
V_b = π × h ÷ 3 × (R² + R × r + r²)R = bell radius, r = tube radius, h = bell height.
Tube
V_t = π × r² × HH is tube height above the bell.
Total
V = V_b + V_tBell and tube do not overlap.
Worked example: 10 in tube, 24 in bell, 12 in bell height, 36 in tube
- R = 1.0 ft, r = 0.4167 ft, h = 1.0 ft
- V_b = 3.1416 × 1 ÷ 3 × (1 + 0.4167 + 0.1736) = 1.665 ft³
- V = 1.665 + 1.636 = 3.302 ft³ → 6 bags
Bell Footing Volume Calculator Conversion Table
The bell footing conversion table lists 5 bell-and-tube combinations with bell, tube and total volumes.
| Tube | Bell dia. × height | Tube height | Bell ft³ | Tube ft³ | Total ft³ | 80 lb bags |
|---|---|---|---|---|---|---|
| 8 in | 20 in × 12 in | 36 in | 1.13 | 1.05 | 2.18 | 4 |
| 10 in | 24 in × 12 in | 36 in | 1.67 | 1.64 | 3.30 | 6 |
| 12 in | 28 in × 16 in | 36 in | 3.06 | 2.36 | 5.42 | 10 |
| 12 in | 30 in × 18 in | 42 in | 3.83 | 2.75 | 6.58 | 11 |
| 16 in | 36 in × 20 in | 48 in | 6.45 | 5.59 | 12.03 | 21 |
Flared plastic footing forms list their own fill volume. Use the label value, if it differs.
What is Bell Footing Volume Calculator?
A Bell Footing Volume Calculator is a concrete calculator for piers with a flared, bell-shaped base, using the frustum formula for the bell and the cylinder formula for the tube.
A bell widens the base of a pier without widening the whole column. Plastic flared footing forms snap onto a tube, and hand-dug belled holes flare at the bottom. A 10 in tube on a 24 in bell spreads the load over 3.14 ft² instead of 0.55 ft², a 5.8 times increase.
The bell resists uplift from frost heave, since frozen soil grips the wide base.
What are the uses of Bell Footing Volume Calculator?
There are 4 main uses of the Bell Footing Volume Calculator.
Flared plastic forms
Builders fill bell forms attached to tubes.
Frost uplift resistance
Designers size bells to anchor piers against heave.
Belled holes
Crews pour hand-dug holes flared at the base.
Bearing upgrades
Contractors add bearing area on soft soil.
🔗Related Sonotube Calculators
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Square Footing Volume Calculator
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Tube and Round Footing Calculator
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Tube and Square Footing Calculator
Add a tube to a square base below it.