Grain Bin Calculator
Estimate grain storage volume, US dry bushels, and mass for round or rectangular bins.
On this page
CalculatorHow to useFormula & methodWorked exampleSeparate the simple shapesBushels, packing, and grain weightFrequently asked questionsRelated calculatorsSourcesHow to use this calculator
- Choose a round or rectangular bin and enter dimensions in one unit.
- Use the actual filled straight-wall depth. Enter zero for top or hopper sections that are absent or empty.
- Enter grain test weight in pounds per US dry bushel to estimate mass as well as volume.
Formula and method
For the assumptions behind these results, read the explanation below. You can also explore Animal Mortality Rate and Feed Conversion Ratio.
A worked example
A rectangular fill measuring 20 × 10 × 10 ft occupies 2,000 ft³. At about 0.803564 US dry bushels per ft³, capacity is about 1,607.13 bushels, with mass determined by the entered test weight.
Separate the simple shapes
The straight section is a cylinder or rectangular prism. A fully filled pointed top or hopper adds a cone or pyramid with the same base area; each contributes one third of base area times its own vertical height. This is a geometric model of the grain, not merely the outside building.
Set unused dimensions to their defaults or any positive value; only dimensions for the chosen shape are used. A curved dome, truncated hopper, off-center pile, or irregular fill does not match this simple pointed-section assumption and requires a different volume calculation.
Bushels, packing, and grain weight
The bushel conversion here uses the defined US dry bushel of 2,150.42 cubic inches, rather than an approximate commercial bin factor. This can differ from reference tools that fold packing assumptions into their bushel constant. Reporting the exact basis keeps the geometry and the grain assumptions separate.
Volume alone does not establish grain mass. The test-weight entry supplies the mass per bushel for the grain under consideration. Moisture, compaction, and grain condition influence practical storage estimates, so compare with measured deliveries or calibrated bin records when making inventory decisions. Structural loading limits are a separate engineering question.
Frequently asked questions
Is this an Imperial bushel?
No. The output is explicitly US dry bushels. Other bushel definitions should not be substituted into the weight calculation.
Can I enter a partially filled bin?
Yes. Enter the measured grain depth rather than the full wall height, and include only top or hopper sections actually occupied by grain.
Why might a supplier list a different capacity?
Nominal capacity may assume a particular peak, packing factor, freeboard, or bushel convention. Compare those assumptions with the dimensions entered here.
Sources and further reading
- NIST Handbook 44 (2015), Appendix C: units of capacity ↗
Government measurement reference, Appendix C page C-17: one US struck dry bushel is exactly 2,150.42 cubic inches.
- OpenStax, Rice University: Prealgebra 2e, volume and surface area ↗
Textbook formulas for rectangular-solid, cylinder, and cone volumes; geometric volume alone does not establish usable capacity.
- National Institute of Standards and Technology — SI conversion factors ↗
Reference for physical unit conversions. The calculator converts measurements before applying its formula.
Our explanations are written for BiologyCalc. Read how we build and check our tools. These calculations are educational estimates where the underlying model requires assumptions.