Concrete Pier Calculator — m, cm to m³, bags, cost
How to use this calculator
Enter the number of piers, choose round (sonotube) or square shape, set the diameter or side length and depth. Choose the unit (m, cm, or mm) from the dropdown next to each input. Use quick-select buttons for common sonotube sizes. Optionally add a flared bell footing at the base. Results update instantly.
Cost — pick ready-mix delivery per m³, 50 kg bags, or 25 kg bags. Select your currency (EUR, PLN, CZK, SEK, etc.) in the settings below.
Reinforcement — vertical rebar per pier with ties, per EN 1992-1-1 (Eurocode 2).
Labor — rate per pier, per m³, or a flat price. Grand total sums all active sections.
Saved Calculations
| Time | Shape | Piers | Size | Depth | Vol m³ | Bags | Cost | Total |
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How to Calculate Concrete for Piers and Sonotubes (Metric)
This concrete pier calculator estimates volume in cubic meters, number of pre-mixed bags (25 kg and 50 kg), total weight in kilograms, material cost, reinforcement requirements, and labor expenses for round sonotubes and square piers. Enter dimensions and choose the unit (m, cm, or mm) from the dropdown, set the depth (standard: 90 cm for frost line, 100 cm standard, 120 cm deep frost), number of piers, and adjust waste allowance from 5% to 20%.
Formulas
Round pier: V = pi x (d/2)² x h. Square pier: V = s² x h. Bell footing (frustum): V = (pi x h / 3) x (R² + R x r + r²) where R = flare radius and r = pier radius. A 50 kg bag covers approximately 0.024 m³ and a 25 kg bag covers approximately 0.012 m³. Concrete density is 2,400 kg/m³.
Reinforcement per EN 1992-1-1 (Eurocode 2)
Choose vertical rebar Ø8 through Ø20 (B500B) with 2 to 6 bars per pier, plus horizontal tie wire hoops. The calculator accounts for concrete cover per exposure class (XC1–XC4, XD/XS per EN 1992-1-1 §4.4.1) and standard development length. Standard bar length is 6 m.
Frequently Asked Questions
How deep should piers be? Piers must extend below the frost line, which varies by region. Common depths range from 80 cm to 120 cm in Central Europe. Check local building codes for exact frost line depth requirements.
When to use a bell footing? A flared (bell) base is required when soil bearing capacity is low or when pier loads are heavy. The wider base distributes weight over a larger area. Typical flare diameters are 1.5x to 2x the pier diameter.
