Building or buying storage that's too small forces you to sell grain immediately after harvest when prices are typically lowest, while oversized storage wastes construction cost. This calculator estimates the grain weight capacity of your storage structure based on its dimensions and the grain's bulk density.
For cylindrical silos: Volume = π × (Diameter ÷ 2)² × Height. For rectangular storage: Volume = Length × Width × Height. Storage Capacity (kg) = Volume (m³) × Bulk Density (kg/m³), adjusted slightly downward for moisture content since wetter grain is denser but less can safely be packed due to spoilage risk.
| Grain | Bulk Density (kg/m³) |
|---|---|
| Wheat | 770-790 |
| Rice (paddy) | 560-580 |
| Maize | 720-740 |
| Soybean | 720-770 |
For a cylindrical silo 12 feet (3.66m) in diameter and 20 feet (6.1m) tall, storing wheat at 780 kg/m³: Volume = π × (1.83)² × 6.1 ≈ 64.1 m³. Capacity = 64.1 × 780 ≈ 50,000 kg (50 tonnes) of wheat — useful to know before deciding whether one large silo or several smaller units better fits your harvest volume and cash-flow needs across the season.
Bulk density depends on grain shape, size, and how tightly individual kernels pack together — rounder, smaller grains like paddy rice leave more air gaps than denser wheat kernels, resulting in noticeably lower weight per unit volume for the same storage space.
No — leaving 10-15% headspace is standard practice to allow for grain settling, aeration airflow, and safe access during loading and unloading, so practical usable capacity is somewhat below the theoretical full volume.
Higher moisture grain is technically denser (more water weight per volume) but should never be packed to full calculated capacity, since wetter grain needs more airflow space to prevent hotspots and mold — always dry grain to safe moisture before maximizing storage fill.
Cylindrical silos generally handle grain pressure and aeration more evenly and are the standard for larger volumes, while rectangular storage (bins, warehouses) is often more practical for smaller volumes or when combined with other storage uses in the same structure.