Grain Bin Capacity Calculator
Estimate the amount of grain in a round or rectangular bin. Enter the bin dimensions and grain depth, then allow for a level, peaked or coned-down grain surface. Results are shown in US bushels, cubic feet and cubic metres.
Calculate grain bin capacity
Estimated grain capacity
Calculation breakdown
| Bin shape | — |
|---|---|
| Base area | — |
| Level-fill volume | — |
| Surface adjustment | — |
| Total volume | — |
| Bushel conversion | — |
This is a geometric estimate. Actual stored grain can differ because of compaction, packing, moisture, test weight, wall corrugations and the true shape of the grain surface.
How grain bin capacity is calculated
For a round bin with level grain, the calculator first finds the cylindrical volume using π × radius² × grain depth. A US bushel is a unit of volume, so the resulting cubic feet are converted to bushels. For a peaked surface, the extra grain is approximated as a cone and added. For a coned-down surface, the missing cone is subtracted.
For rectangular bins, the level volume is length × width × grain depth. A peaked or coned-down surface is treated as a pyramid over the rectangular base, using one-third of base area multiplied by the vertical surface height.
Round grain bin formula
A quick extension formula often used for level round bins is approximately bushels = 0.628 × diameter² × grain depth, with dimensions in feet. This calculator uses the underlying geometric volume and the US bushel volume conversion, which gives essentially the same practical estimate while also supporting metric dimensions and non-level grain surfaces.
What measurements should I use?
Use the inside diameter, length or width wherever possible. Grain depth should be the actual vertical depth at the wall. If the grain peaks in the centre, enter the vertical distance from the wall-level grain surface to the top of the peak. If the centre is lower after unloading, select coned down and enter the corresponding vertical drop.
US bushels and grain weight
This calculator estimates volume, not grain weight. Different crops and grain lots can have different test weights, moisture contents and packing characteristics. If you need inventory by weight, use the measured test weight or scale records rather than assuming that every bushel has the same mass.
Frequently asked questions
How many bushels are in a cubic foot?
One US bushel is about 1.24446 cubic feet, equivalent to about 0.80356 US bushels per cubic foot. These conversions are based on dry-volume measurements published by the National Institute of Standards and Technology (NIST) .
Should I include the roof height?
Only include grain that is actually present. Do not enter the roof height as grain depth. If grain forms a peak above the sidewall grain level, use the peaked-surface option and enter the height of that grain peak.
Why might the result differ from the manufacturer's bin rating?
Manufacturer ratings can use specific construction dimensions and stated capacity conventions. A field measurement also includes uncertainty from grain shape, compaction and how dimensions are measured. Treat this calculator as an estimate and use the manufacturer's capacity chart when an official rated capacity is required.