Grain Bin Volume: How to Calculate Your Storage Capacity…

Q: How many bushels does a 30-foot grain bin hold?

A 30-foot diameter bin with 20-foot sidewall height holds roughly 11,300 bushels at level fill (no peak). Adding a peaked cone of 8 feet adds approximately 2,800 bushels. Use the grain bin volume calculator with your exact measurements for your bin.

Q: How do I calculate bushels in a flat storage building?

Flat storage uses length × width × average grain depth in cubic feet, divided by 1.2445 cubic feet per bushel (USDA standard). Account for sloped grain surface — average depth is less than wall height. Many flat buildings are measured in tons rather than bushels.

Q: What is the difference between bin capacity and usable storage?

Nameplate capacity assumes level fill to the eave. Usable storage accounts for peak, aeration floor dead space, and safety margin below the roof. You typically cannot fill to the physical top safely — plan 5–10% below calculated maximum for aeration headspace.

Q: How much does a bushel of corn weigh?

Standard test weight is 56 lb/bu. Soybeans are 60 lb/bu, wheat 60 lb/bu. Test weight affects tons stored and truckloads — not cubic bushel capacity. A bin holds the same bushels regardless of test weight; weight changes with grain density.

Before harvest, you need to know how many bushels you can actually store — not your best guess. Storage capacity drives your store-vs-sell decision, whether you need commercial overflow, and whether you have overpromised on forward contracts.

The grain bin volume formula

A typical upright grain bin is a cylinder plus a cone peak on top. The math:

Cylinder volume = π × r² × h (radius and sidewall height in feet)

Cone peak volume = (1/3) × π × r² × peak height

Bushels = total cubic feet ÷ 1.2445 (USDA standard cubic feet per bushel)

Example: 40-foot diameter bin (20-foot radius), 24-foot sidewall, 6-foot peak:

Cylinder: π × 20² × 24 = 30,159 cu ft
Peak: (1/3) × π × 20² × 6 = 2,513 cu ft
Total: 32,672 cu ft ÷ 1.2445 ≈ 26,250 bushels

Or skip the math — use the grain bin volume calculator to enter diameter, height, and peak height for instant results.

What measurements do you need?

Three numbers:

Bin diameter — inside diameter at the widest cylindrical point
Sidewall height — floor to where the cone starts (not to the roof peak)
Peak height — grain peak above the eave if you fill peaked (optional but significant)

Measure from inside the bin rings if possible. Safety first — do not climb a full bin. Manufacturer specs on the nameplate give diameter and eave height; peak is what you measure in the field at harvest fill.

Grain type affects bushels only for weight estimates

Corn at 56 lb/bu vs. soybeans at 60 lb/bu does not change cubic feet capacity. It only changes tons stored and truckload weights. Bushels are the marketing unit; tons matter for shipping and bin structural load.

When you run the calculator, optional test weight converts bushels to estimated pounds for logistics planning.

Bin capacity vs. actual fill — accounting for peak

Most bins are not filled flat to the eave. A peaked load adds 10–15% capacity over level-fill nameplate ratings. Common mistake: measuring only the cylindrical portion and missing the cone — then running out of room mid-harvest.

Plan usable storage below calculated maximum. Leave headspace for aeration and safety. A bin rated at 25,000 bushels level-fill may hold 28,000+ peaked — but your aeration fan was sized for 25,000.

What the bin manufacturer says vs. what the calculator says

Manufacturer ratings assume level fill to the eave — no peak. Field measurement with peak typically gives more capacity than the nameplate. Aeration floor plenum and sump subtract small amounts.

If your calculator result and nameplate disagree, trust your field measurements for harvest planning and the nameplate for aeration design limits.

Before you fill — three things to check

Does moisture match what your bin can store safely? Use the grain moisture calculator — convert wet bushels to dry equivalents before you fill. Storing 20% corn when your aeration system was designed for 15% dry grain is a management problem, not a math problem.
Is your aeration system adequate for the moisture you are putting in? Capacity without airflow is a spoilage bin.
Is the bin structurally sound for the weight? Check rings, foundation, and roof condition before peak harvest pressure.

Integrating bin volume into your harvest marketing decision

Knowing capacity before harvest is step one of the store vs sell decision. You cannot store what you do not have room for, and you cannot forward contract what you will not produce.

Run your expected production through the crop breakeven calculator alongside storage capacity. If breakeven is $3.50 and harvest price is $4.20 but bins are full, commercial storage or an early sale may beat paying overflow fees.

Grain bin volume FAQ

How many bushels does a 30-foot grain bin hold?

Roughly 11,300 bu level-fill at 20-foot sidewall; more with peak. Use the calculator for your bin.

How do I calculate bushels in a flat storage building?

Cubic feet ÷ 1.2445. Use average grain depth, not wall height.

What is the difference between bin capacity and usable storage?

Nameplate vs. peak fill and aeration headspace. Plan below calculated max.

How much does a bushel of corn weigh?

56 lb/bu standard test weight.