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Grain Bin Storage Calculator
Bushels, pounds, tons and floor load for a round bin from diameter and depth, with a safe-moisture margin by grain.
Grain Bin Storage Calculator
Chlorova · updated for 2026
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Bushel weights are the standard shrink-out test weights used for planning, and your grain measures lighter when it is thin, unripe or weedy. Storage capacity also depends on bin taper, the cone of grain above the eave and how level the floor truly is, so treat the bushel figure as a fill-line estimate rather than a scale reading. Floor load is the number that gets people hurt: grain weighs roughly 45 to 60 lb per cubic foot, which means depth alone drives the poundage and a shallow wide bin can be far safer on a domestic slab than a tall narrow one. Confirm any structure with the engineer or the manufacturer's load plate before filling it.
A grain bin is sized by the bushel and loaded by the pound, and the second number is the one that fails a floor. Bushel weight varies enormously by grain, from 32 lb for oats to 60 lb for wheat and soybeans, so the same bin carries wildly different tonnage depending on what you actually grow. Moisture is the other silent variable, because grain stored above its safe line spoils rather than keeps. This calculator turns diameter and depth into bushels, pounds, floor load and a drying margin.
Sizing the Bin and the Floor
- Choose the grain, which sets both weight and safe moisture.
- Measure the inside diameter, not the outside shell.
- Enter the depth of grain you intend to hold, to the fill line.
- Set the moisture the tester reads on the day of filling.
- Use a real floor rating, not a hopeful guess about the slab.
- Read bushels first, since that is the buy or sell number.
- Then check floor load against the share-of-rating verdict line.
- Trim depth until the allowed-depth line clears your fill line.
- Compare moisture to the safe target before drying decisions.
- Split the harvest into shallow bins if the floor is the limit.
Cubic Feet, Bushels, Pounds
A round bin is a cylinder, so floor area is pi times radius squared, and a 12-foot diameter gives about 113 square feet. Multiply by grain depth for volume: 113 times 8 is roughly 905 cubic feet. One bushel of shelled grain is 1.2445 cubic feet, so volume times 0.8037 returns bushels, about 727 in this bin.
Weight follows from the standard bushel figure for the grain, 56 lb for corn, so 727 bushels come to 40,722 lb, or just over twenty tons. Floor load is that weight divided by the same floor area, and the depth cancels out neatly: load per square foot equals grain depth times the roughly 45 lb per cubic foot bulk density. That is why a floor limit converts straight back into a safe depth by dividing the rating by bulk density.
Worked Example: A 12-Foot Corn Bin
- Pick corn, with a diameter of 12 ft and 8 ft of grain.
- The floor area prints 113.1 sq ft from pi r squared.
- Volume is 113.1 times 8, so about 905 cubic feet.
- Divided into bushels that is 727 bu of shelled corn.
- At 56 lb per bushel, grain weight reaches 40,722 lb.
- In tons the line reads 20.36, a serious truckload.
- Floor load works out at 360 lb per square foot.
- Your slab is rated 100, so the share reads 360%.
- The verdict says engineered grain floor, not a shop slab.
- Allowed depth is 100 divided by 45, so 2.2 ft.
- Moisture 15% against a 15% target leaves zero margin.
- The moisture verdict asks for aeration to even it out.
Weights and Safe Moisture by Grain
Standard planning figures for shelled grain at average test weight. Bulk density is the weight of one loose cubic foot, which is what actually loads a floor, and safe moisture is the long-storage target for grain held through winter in temperate air.
| Grain | lb per bushel | lb per cu ft | Safe moisture | Tons in a 12x8 bin |
|---|---|---|---|---|
| Corn | 56 | 45.0 | 15% | 20.4 |
| Wheat | 60 | 48.2 | 13.5% | 21.8 |
| Soybean | 60 | 48.2 | 13% | 21.8 |
| Barley | 48 | 38.6 | 13.5% | 17.5 |
| Oats | 32 | 25.7 | 13% | 11.6 |
| Rye | 56 | 45.0 | 14% | 20.4 |
Key Terms
- Test weight
- Pounds per measured bushel, the classic check on grain maturity and plumpness.
- Bulk density
- Weight of one loose cubic foot, which is what multiplies depth into floor load.
- Safe storage moisture
- The moisture percentage at which grain keeps without heating or mold growth.
- Aeration
- Pulling ambient air through a bin to even temperature and stop condensation.
- Equilibrium relative humidity
- The air humidity at which grain neither gives up nor takes on moisture.
- Floor load
- Total grain weight spread over the bin footprint, in pounds per square foot.
What Actually Buries a Floor
- Depth rather than diameter decides floor load, since pounds per square foot is bulk density times depth: a wide shallow bin of oats can be gentler on a slab than a narrow column of wheat.
- A residential garage slab is built for a car's wheel, a concentrated load, and not for a continuous 360 lb per square foot press across a whole footprint, which is a separate engineering case.
- Moisture at fill is a snapshot, not a promise: grain rewets from humid autumn air and can gain a full point in the bin after a good drying run.
- Spoilage costs are not evenly shared: one wet pocket or a nest of weedy seed can carry mold through a whole bin, which is why cleaning and aeration beat a faster fill.
- Grain bridges and avalanches are a fatal hazard rather than a joke, and no calculator makes entering a partly full bin safe without a harness and a spotter.
Common Mistakes & Fixes
- Reading the bushel figure as if it were a weight, then overloading a floor.
- Using an outside diameter, which inflates capacity on any lined or ribbed bin.
- Assuming a garage slab was designed for continuous grain pressure.
- Storing at the moisture the dryer stopped on rather than the tested number.
- Filling to the eave and ignoring the extra cone of grain above it.
- Blending a wet load with a dry one instead of drying the wet one.
- Skipping aeration because the grain felt cool on the day it went in.
When to Reach for This
Use it before you buy or build a bin, when planning how much of a market-garden or small-acreage grain harvest will fit, and whenever an existing slab is being considered as a bin pad, since the depth-your-floor-allows line settles that argument quickly. For a harvest still in the ground, start with the garden yield estimator and the feed-a-family planner, and use this tool at the point where volume becomes weight and weight becomes a structural question.
Grain Bin Storage Calculator: Frequently Asked Questions
How many bushels fit in a round grain bin?
Calculate the floor area, multiply by grain depth, then divide by 1.2445 cubic feet per bushel. A 12-foot bin eight feet deep holds roughly 727 bushels of shelled grain, before you account for the cone that stacks above the eave in a peaked-bin situation.
How heavy is a full grain bin?
Weight is bushels times the standard weight for that grain, so 727 bushels of corn at 56 lb comes to about 40,700 lb, or 20 tons. Wheat and soybeans at 60 lb per bushel push the same bin past 21 tons, while oats at 32 lb come in at under 12.
What floor load can a concrete slab take?
A typical residential garage slab is designed for vehicle wheel loads rather than uniform pressure, and continuous grain loading is a separate engineering case. Treat 100 lb per square foot as an optimistic domestic figure, because grain eight feet deep imposes roughly 360.
Why does oats weigh so much less than wheat?
Bushel weights are standard volume measures, and a bushel of oats is defined at 32 lb while wheat is 60 lb, reflecting the lighter, huskier kernel and how it pours. Bulk density matters just as much: oats load a floor at about 26 lb per cubic foot against wheat's 48.
What moisture should grain be stored at?
Roughly 13% for oats and soybeans, 13.5% for wheat and barley, 14% for rye and 15% for corn, assuming temperate storage with aeration. Holding grain hotter or longer than one season calls for a lower number, and the calculator prints the margin so you can see the gap.
Does aeration fix grain that went in too wet?
Aeration evens temperature and prevents condensation, and enough outside air can pull a little moisture down. It will not rescue a load several points over the safe line, and that grain should be dried properly or eaten first.
Can I use this for a grain silo or a hopper?
The cylinder math holds for any straight-walled round container, so a bucket, drum or tank works if you enter inside diameter and true depth. Conical hoppers and square bins have different geometry, so measure their volume separately.
Sources & Further Reading
- Grain Inspection, Packers and Stockyards Administration, Handbook 100 Book II — USDA. Standard weights per bushel for shelled grain.
- Managing Stored Grain: Moisture, Temperature and Aeration — University of Nebraska-Lincoln Extension. Basis for safe storage moisture and aeration practice.
- On-Farm Grain Storage and Handling — Kansas State University Agricultural Extension. Supports bulk density and floor-load guidance.
Chlorova Gardening Team
Builds, checks and documents every tool we publish
Chlorova editorial review
Checked against extension-service publications
Formula verified against published references · Updated
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