How to Calculate Concrete of Pier and Caisson

Piers and caissons are deep foundation elements used where soil conditions require heavy load-bearing capacity. Both are cylindrical in shape, and their volume is based on simple geometric formulas. Below is a practical workflow to calculate pier or caisson concrete accurately, including for belled bases and waste allowance.

Step 1: Work in Consistent Units

Convert all inputs to a single system before calculating. In metric, use meters for depth and diameter; in imperial, convert inches to feet. This prevents errors in final volume.

Step 2: Apply the Cylinder Formula

For a straight shaft pier or caisson, volume is calculated as: V = π × r² × h, where r is radius and h is depth.

Example (Metric): D = 1.2 m, h = 10 m → r = 0.6 m → V = 3.1416 × 0.6² × 10 = 11.31 m³.

For 6 piers: 11.31 × 6 = 67.86 m³.

Step 3: Include a Belled Base if Applicable

Caissons often have a widened base for added stability. Use the frustum formula: V = (πh / 3) × (R₁² + R₁R₂ + R₂²) where R₁ is the top radius and R₂ is the bottom radius of the bell.

Step 4: Multiply by Quantity

Multiply the per-unit concrete volume by the total number of piers or caissons required for your foundation plan.

Step 5: Add Waste Allowance

Always add 5–10% extra to account for over-excavation, spillage, or pump line losses. This ensures you won’t fall short on pour day.

Conversion Tips

1 m³ = 35.315 ft³
1 m³ = 1.308 yd³
Always order in supplier-preferred units (m³ or yd³).

Common Mistakes to Avoid

Mixing metric and imperial units.
Forgetting to include belled base volume.
Not adding waste allowance.

In summary: calculate shaft volume with V = πr²h, add bell volume if required, multiply by number of units, and include 5–10% waste. A pier/caisson calculator makes this process faster, reduces human error, and ensures you order the right amount of concrete for your foundation.