Grain Bin Calculator

Estimate the storage capacity of your bins for harvest planning.

Height of the vertical wall, not including the roof peak.
Height from the eave line to the very top peak. Enter 0 if filled only to eaves.
Grain at the bottom of tall bins compresses, increasing capacity slightly.

Estimated Capacity:

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Total Bushels
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Est. Weight (Tons)
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*Based on standard test weights and volume corrections.

Maximizing Every Bushel: A Guide to Grain Bin Management

For farmers, the harvest doesn't end when the combine stops rolling. It ends when the grain is safely stored, managed, and eventually sold. Understanding the exact capacity of your grain bins is crucial for logistics, insurance, and inventory management. Whether you are storing corn, soybeans, or wheat, our Grain Bin Calculator helps you estimate your holding capacity with precision.

How Grain Bin Capacity is Calculated

Calculating the volume of a grain bin involves simple geometry, but calculating the bushels involves agricultural physics.

1. The Cylinder (Main Body)

Most bins are cylinders. The volume formula is:

Volume = π × r² × h

Where r is the radius (half the diameter) and h is the eave height.

2. The Cone (Peak)

Grain naturally piles in a cone shape at the angle of repose (typically 23-28 degrees). If you fill the bin to the peak, you gain significant capacity.

Cone Volume = (π × r² × Peak Height) / 3

3. The Bushel Conversion factor

Volume in cubic feet must be converted to bushels. The standard US Winchester Bushel is approximately 1.244 cubic feet. Therefore:

Bushels = Cubic Feet × 0.8036

4. The "Pack" Factor

This is where it gets tricky. Grain isn't a liquid; it's a granular solid. In deep bins, the weight of the grain on top compresses the grain on the bottom, increasing the density. A tall bin might hold 5-7% more grain than the geometric volume suggests due to this compaction. Our calculator includes an option to estimate this packing factor.

Standard Test Weights

Capacity is often discussed in "wet bushels" or volume bushels, but sales are based on weight. Standard test weights per bushel are:

  • Corn: 56 lbs
  • Soybeans: 60 lbs
  • Wheat: 60 lbs
  • Oats: 32 lbs
  • Barley: 48 lbs

If your corn test weight is lighter (e.g., 54 lbs), the bin will technically hold the same volume, but fewer tons of grain.

Safety First: The Rules of Grain Bins

Grain bins are essential tools, but they are also deadly hazards. Hundreds of entrapments occur annually.

"Flowing Grain" Entrapment

It takes only 4 seconds for a person to be trapped waist-deep in flowing grain, and about 20 seconds to be fully submerged. Never enter a bin while the unload auger is running. Use "lock-out/tag-out" procedures to ensure power is off.

"Bridging"

Moldy grain can fuse together, creating a hard crust on top with empty space underneath. If you walk on this "bridge," it can collapse, burying you instantly.

"Avalanche"

Grain stuck to the side of a bin can fall suddenly if dislodged, burying anyone standing below.

Bin Management Tips

  1. Core the Bin: Remove the center core of grain shortly after filling to remove fines (small particles) that accumulate in the center and block airflow.
  2. Monitor Temperature: Hot spots indicate insect activity or mold. Use temperature cables if available.
  3. Maintain Moisture: Storing corn at 15% is usually safe for winter, but 13-14% is safer for summer storage.

Using This Calculator

  • Diameter: Measure the inside diameter if possible, or outside minus the corrugation depth.
  • Eave Height: Measure to the eaves (the top of the vertical wall), not the peak.
  • Peak Height: If the bin is peaked, estimate the height of the cone above the eaves.

Note: This calculator provides an estimate. Actual capacity varies based on moisture content, debris, and leveling.