Grain Bin Calculator
Enter the bin diameter and grain depth, with a peak or drawn-down cone, and get standard bushels using the Iowa Department of Agriculture's grain measuring method.
Leave blank to use Iowa's rule of thumb.
For an estimated weight.
The result updates as you type.
Grain in the bin
10,796 standard bushels
568.2 bushels per foot of depth · 13,430 ft³
| Level portion | 9,660 bu |
| Peak (height ÷ 3 × bushels per foot) | +1,136 bu (6 ft, rule of thumb) |
What this page cannot tell you
How tightly the grain has packed, its moisture, or its test weight's effect on bushel count. Iowa's guidance notes corn over 54 lb/bu and soybeans over 56 lb/bu give more bushels than standard, and that pack charts (from County Extension) are needed for higher accuracy. Measure depth at several points around a peaked or drawn-down bin.
How to estimate bushels in a grain bin
- Measure the diameter. Inside diameter of the round bin, in feet.
- Measure depth at the side wall. From the floor to the grain surface at the wall.
- Describe the top. Level, peaked, or drawn down into a cone; enter the height or depth, or leave it blank for Iowa's rule of thumb.
- Read the bushels. Standard bushels, bushels per foot and cubic feet.
10 situations where a grain bin calculator helps
Inventory for a marketing plan
Know how many bushels you have before pricing sales.
Crop insurance and loan paperwork
Measured bushels for program documentation.
Planning harvest space
Bushels per foot shows how much a bin holds per foot of fill.
After unloading part of a bin
The drawn-down cone option subtracts the hollow.
Peaked bins
Add the cone on top, measured or by rule of thumb.
Comparing bins
Try different diameters to see capacity per foot.
Estimating truckloads
With a test weight, get tons to plan hauling.
Landlord or partner splits
A common, documented method for dividing stored grain.
Checking a bin's rated capacity
Compare the manufacturer's figure with the measured volume.
Teaching farm math
Every step of the official method is shown.
Where the method comes from
The method is the Iowa Department of Agriculture and Land Stewardship Grain Warehouse Bureau's 'Guidelines on measuring grain': diameter × diameter × depth × 0.7854 gives cubic feet, and × 0.80385 gives standard bushels. Bushels per foot of depth = diameter² × 0.7854 × 0.80385.
A peak adds 'the height of the peak above the base divided by 3 and multiplied times the bushels per foot' — the volume of a cone. If the peak height isn't known, Iowa's rule of thumb is 0.4 × the bin's radius for corn and 0.5 × the radius for soybeans. For grain drawn down into a cone-shaped hollow, the same one-third rule is subtracted from the depth measured at the wall.
Limits: standard bushels are a volume measure. Iowa notes that corn over 54 lb per bushel and soybeans over 56 lb per bushel yield more bushels than standard, and that pack charts — available through County Extension — are needed for higher accuracy, because grain packs down in tall bins. Weight here is bushels × the test weight you enter. Everything runs in your browser.
Sources
- Iowa Department of Agriculture and Land Stewardship — Guidelines on measuring grain — 0.7854 × 0.80385, peak ÷ 3, corn/soybean rules of thumb
Frequently asked questions
How many bushels are in a 30 ft bin per foot?
30 × 30 × 0.7854 × 0.80385 = 568 bushels per foot of depth.
How do I calculate bushels in a round bin?
Diameter² × depth × 0.7854 × 0.80385. Add one-third of the peak height times bushels per foot for a peaked bin.
How do I estimate the peak if I can't measure it?
Iowa's rule of thumb: 0.4 × the radius for corn, 0.5 × the radius for soybeans.
What's a standard bushel?
A volume unit; 0.80385 standard bushels per cubic foot in Iowa's method.
Why does my bin hold more than this says?
Grain packs down in tall bins. Pack factors from Extension tables adjust for that.
Can I get the weight?
Enter the test weight in pounds per bushel; the page multiplies it out.
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