Grain Bin Capacity Calculator

Frequently Asked Questions

Why is the bushel factor 0.8036?

A struck (level) bushel occupies 1.2445 cubic feet, so each cubic foot holds 1 ÷ 1.2445 ≈ 0.8036 bushels. This figure is baked into every grain capacity chart and bin manufacturer's table.

Does grain type change the bushel factor?

The volume-to-bushel factor is constant, but test weight and moisture affect how many marketable bushels and how much actual weight that volume represents. Wet grain at 20% moisture occupies the same space as dry grain but delivers fewer marketable bushels after shrinkage.

What about the peaked cone of grain above the eave?

A full bin usually carries a cone of grain above the eave. Add it separately with a cone volume formula (1/3 × π × r² × cone height) if you need a precise full-bin figure. For partial-fill estimates this is usually unnecessary.

Should I trust this over my bin manufacturer's chart?

The math matches a level cylinder exactly, but your manufacturer's chart accounts for floor slope and hopper geometry. Use both and reconcile. Measure the inside diameter carefully - an inch of diameter error compounds significantly because capacity grows with the square of the radius.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

A round grain bin is just a cylinder, and its capacity is pure geometry once you know the diameter and how deep the grain sits inside it. This calculator computes the cylinder's volume in cubic feet from the bin's inside diameter and the depth of grain, then converts that volume to bushels using the standard factor of 0.8036 bushels per cubic foot - the dry, struck (heaped-level) bushel that every elevator and grain table is built around. Enter the full bin height for total capacity, or the current grain depth to see how much is in storage right now.

Formula and Method

Volume (cubic ft) = π × (diameter ÷ 2)² × grain depth, the standard cylinder formula with radius equal to half the diameter. Bushels = volume (cubic ft) × 0.8036, where 1.2445 cubic feet equals one struck bushel, so its reciprocal 0.8036 converts the other way. Use the bin's inside diameter and the actual grain depth, not the bin's overall height, unless the bin is full. The tool rejects zero or negative dimensions.

Note this gives the cylindrical (sidewall) capacity only. Any coned grain peaked above the eave adds extra and any sloped floor or hopper subtracts - consult your bin chart for those adjustments.

Worked Example

A 24 ft diameter bin filled to a grain depth of 20 ft. Radius = 12 ft, so volume = π × 12² × 20 = π × 144 × 20 ≈ 9,048 cubic feet. Bushels = 9,048 × 0.8036 ≈ 7,271 bushels. Drop the grain depth to 10 ft and the bin holds about half that, 3,635 bushels - capacity scales straight-line with depth but with the square of diameter, which is why a small jump in bin width adds so much storage.

Common Mistakes

Using bin height instead of actual grain depth when estimating what is currently stored.

Measuring outside diameter; the steel wall is thin but you want the inside dimension for grain volume.

Forgetting the coned peak when a bin is overfilled - that heap can add several hundred bushels.

Ignoring a hopper bottom or aeration floor, which reduces usable volume below the sidewall calculation.

Applying the 0.8036 factor to wet grain and treating the result as marketable dry bushels.

Grain Bin Management Tips

The diameter-squared scaling is the most important thing to understand about bin capacity: doubling the diameter quadruples the volume at any given depth. This is why a 36 ft bin stores dramatically more than two 24 ft bins at the same depth. When monitoring stored grain, check temperature cables weekly during the first month after filling - hot spots indicate moisture migration and potential spoilage. Aeration fans should maintain grain temperature within 10-15 degrees of outside temperature to slow moisture movement. Use the inside diameter measured at the bottom ring, not the nominal bin size printed on the order sheet, for the most accurate calculation. Manufacturer capacity charts account for floor slope and hopper geometry, so use them alongside this calculator and reconcile any difference.

Grain Bin Capacity Calculator

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