Grain Bin Calculator

A grain bin calculator estimates the geometric volume of a storage bin and translates that space into usable grain capacity. This version handles a straight cylinder, a cylinder with a cone bottom, or a cylinder with both top and bottom cones. The cylinder volume is pi times radius squared times height. Each cone contributes one third of pi times radius squared times its vertical height. Measurements should represent the inside dimensions available to grain, not the outside diameter or overall structure height. For imperial entries, feet are converted to meters before volume is calculated. The result therefore provides a consistent cubic-meter value, an approximate number of US bushels based on the standard bushel volume, and an estimated metric weight. A fill percentage reduces the geometric volume to account for headspace or an intentionally partial load. Weight depends on bulk density, which varies by crop, variety, moisture, foreign material, compaction, and test weight. The calculator uses representative densities of 780 kilograms per cubic meter for wheat, 720 for corn, 750 for soybeans, 620 for barley, and 430 for oats. Those values are useful for planning but should not replace a measured test weight when inventory, structural loading, contracts, or transportation limits require precision. Bin shape also matters. Ignoring a hopper bottom or grain held under a conical roof can create a meaningful capacity error. Measure cone height vertically from its base plane to its point, and use the same diameter as the cylinder only when the cone spans the full bin. Irregular floors, aeration equipment, ducts, wall corrugations, and a peaked grain surface can make actual capacity differ from ideal geometry. The bushel result is a volume conversion, not a crop-specific legal test-weight conversion. Grain markets often associate a standard number of pounds with a bushel of each commodity, while a physical bushel itself is a volume. This tool separately estimates weight from density so users can see both concepts without treating them as interchangeable. Use the estimate for harvest planning, storage allocation, inventory checks, and logistics. Confirm critical figures with calibrated measurements, local grading standards, manufacturer charts, and qualified engineering guidance. Never use a simple capacity estimate as the sole basis for structural loading, confined-space entry, or other safety decisions.