Grain Bin Calculator

First find the bin's interior volume in cubic feet. A round bin is a cylinder: volume = π × (diameter ÷ 2)² × height. A rectangular bin is length × width × height. Then divide the volume by 1.244456, because one US bushel equals 1.244456 cubic feet (2150.42 cubic inches). Example: an 18 ft diameter round bin, 20 ft tall, holds π × 9² × 20 = 5,089.38 ft³, which is 5,089.38 ÷ 1.244456 = 4,089.64 bushels.

An 18 ft diameter round bin that is 20 ft tall holds about 4,089.64 bushels of geometric capacity. At standard corn test weight (56 lb/bu), that is 229,020 lb of corn — 114.51 US short tons (103.88 metric tonnes).

Multiply bushels by the grain's standard test weight in pounds per bushel, then divide by 2,000 for US short tons (or by 2,204.622 for metric tonnes). USDA official test weights: corn 56 lb/bu, wheat 60 lb/bu, soybean 60 lb/bu, grain sorghum 56 lb/bu, barley 48 lb/bu, oats 32 lb/bu. Example: a 21 ft × 25 ft bin holding wheat has 6,958.07 bu × 60 lb/bu = 417,484 lb = 208.74 short tons (189.37 metric tonnes).

A cone (hopper) bottom adds the volume of a cone: (1/3) × π × r² × cone height. A 15 ft diameter bin, 18 ft tall, with a 3 ft cone bottom holds 3,357.58 ft³ = 2,698.03 bushels, versus 3,180.86 ft³ = 2,556.03 bushels with a flat floor — the cone adds about 142.00 bushels. Cone bottoms also self-empty by gravity, which is why hopper-bottom bins are popular for smaller on-farm storage.

Grain settles and packs tighter as a bin fills, so a full bin can hold a few percent more weight than its pure geometric volume suggests — typically around 4–6% for tall bins. This tool applies it as an optional labeled estimate. Example: the 21 ft × 25 ft wheat bin above is 6,958.07 bu geometric; with a 4% compaction estimate it holds 7,236.40 bu (434,184 lb, 217.09 short tons).

Moisture changes weight per bushel, not the bin's geometric volume. Test weights are defined at standard moistures (e.g., corn 56 lb/bu at 15.5% moisture, wheat 60 lb/bu at 13.5%, soybean 60 lb/bu at 13.0%). Wetter grain is heavier per bushel, so the same bin holds more pounds — but buyers discount wet grain for drying, which is why moisture matters for pricing, not for volume capacity. This calculator uses standard test weights; if your grain tests below standard, weigh a sample and enter a custom lb/bu.

Aeration is forcing ambient air through stored grain with fans to control temperature and prevent moisture migration and spoilage. Larger bins (and deeper grain depths) need proportionally more airflow — the standard rule of thumb is 0.1–0.2 cfm per bushel, with higher rates for wet grain. Fan sizing and duct layout depend on bin diameter and grain depth, so knowing your bin's true bushel capacity (from this calculator) is the first step in sizing aeration equipment.

Yes. Enter dimensions in meters and the tool converts them to feet (1 m = 3.28084 ft) before computing volume. Example: a 6 m diameter round bin, 8 m tall (19.69 ft × 26.25 ft), has 7,987.99 ft³ = 6,418.86 bushels, or 359,456 lb of corn (179.73 short tons).

A 30 ft diameter round bin, 40 ft tall, has 28,274.33 ft³ = 22,720.24 bushels of capacity. Filled with grain sorghum (56 lb/bu), that is 1,272,333 lb = 636.17 US short tons (577.12 metric tonnes). Filled with oats (32 lb/bu), the same bin holds 727,048 lb = 363.52 short tons.

Neither — this tool computes storage capacity from bin dimensions (diameter/height or length/width/height) into bushels and grain weight. For converting between grain units (bushels ↔ pounds ↔ kilograms), use our grain unit converter; for harvest yield per acre (bushels per acre from field measurements), use a crop yield calculator. Those answer different questions than bin sizing.