Grain Bin Capacity Calculator
A grain bin capacity calculator estimates how many bushels of grain a round storage bin holds from its diameter and the depth of grain inside. The grain occupies a cylinder, so its volume is pi times the radius squared times the grain height; multiplying that cubic-foot volume by a conversion factor of bushels per cubic foot gives the capacity in bushels. This tool takes the bin diameter and the grain height in feet, computes the cylinder volume, then multiplies by 0.8 bushels per cubic foot (the standard factor for level dry grain) to return the bushels stored. Both the diameter and the height are editable so you can model any bin and any fill level, from a partly filled bin to one filled to the eave. Knowing the bushels helps you track inventory, plan marketing and drying, and confirm a bin is not overfilled. Safe storage also depends on grain temperature and moisture, where the records published by the US National Oceanic and Atmospheric Administration inform aeration decisions. This base calculation covers the cylindrical portion only, not a peaked cone on top. Every figure is computed deterministically from the formula shown below, with a worked example that reconciles exactly to the calculator so you can follow each step yourself.
Bin capacity is the cylinder volume times bushels per cubic foot: bushels = pi x (d/2)^2 x height x 0.8. An 18 ft diameter bin filled to 16 ft holds about 3,257.20 bushels of grain.
Grain bin capacity formula
Volume (cu ft) = pi x (d / 2)^2 x H
Bushels = Volume x 0.8
d = bin diameter (feet)
H = grain height (feet)
0.8 = bushels per cubic foot (level dry grain)
The factor 0.8 bushels per cubic foot applies to level dry grain. A heaped cone on top adds extra volume that this base calculation does not include.
Worked example
A round bin 18 feet in diameter is filled with grain to a height of 16 feet.
- Radius = 18 / 2 = 9 ft
- Volume = pi x 9^2 x 16 = 4,071.50 cu ft
- Bushels = 4,071.50 x 0.8 = 3,257.20 bushels
The bin holds about 3,257.20 bushels. These are the calculator's default inputs, so the result above matches the widget exactly.
Grain Bin Capacity Calculator: frequently asked questions
How many bushels are in a cubic foot?
Level dry grain is conventionally taken as 0.8 bushels per cubic foot, the inverse of the 1.25 cubic feet per bushel standard. This calculator uses 0.8 to convert the cylinder volume in cubic feet into bushels. The factor is the same regardless of grain type for volume-based capacity.
Does this include the cone on top?
No. This base calculation covers the cylindrical column of grain only. A bin filled past the eave forms a cone whose volume (one third times base area times peak height) adds capacity. Add the cone separately if your bin is heaped above the sidewall.
How do I measure grain height?
Measure the depth of grain from the floor to the top of the level surface, in feet. For a partly filled bin, this is less than the bin's full sidewall height. Use the inside diameter, not the outside, for the radius.
Does moisture change the bushel count?
Volume-based capacity does not change with moisture, but the marketable, moisture-adjusted bushels do. Wet grain shrinks when dried to a standard moisture, so the sellable bushels can be fewer. Track moisture separately for marketing, using weather data such as NOAA's to guide drying.
How do I store grain safely?
Keep grain cool and dry, and use aeration to manage temperature and moisture, which prevents spoilage and insect activity. The US National Oceanic and Atmospheric Administration publishes the temperature and humidity records that inform aeration and drying schedules.
Official sources
- Weather and temperature records for safe grain storage: US National Oceanic and Atmospheric Administration (NOAA). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.