How are cubic feet converted to bushels?

One US bushel of dry shelled grain occupies about 1.2445 cubic feet, so bushels equal cubic feet divided by 1.2445, or cubic feet times 0.8036. This is a volume bushel and is the standard used for bin capacity, independent of the grain type.

What is test weight and why does it set the tonnage?

Test weight is the weight of grain that fills a one-bushel measure, such as 56 lb for corn or 60 lb for wheat and soybeans. Multiplying bushels by test weight gives pounds, which convert to tonnes. Denser, drier grain weighs more per volume bushel.

How is a round bin volume calculated?

The cylinder volume is pi times the radius squared times the grain depth. If you fill above the eave into the cone of a peaked roof, add the cone, one-third times pi times radius squared times peak height. This tool covers the cylindrical section and an optional peak.

How do I estimate a free-standing grain pile?

A symmetrical conical pile is one-third times pi times the base radius squared times the peak height. The peak height depends on the grain's angle of repose, roughly 23 degrees for corn and wheat, which the tool can estimate from the base diameter if you do not measure it.

Does this account for packing or moisture?

The volume-to-bushel conversion already reflects typical packing of free-flowing grain. It does not adjust for moisture shrink or for very fine or trashy grain that packs tighter. For weight, use the actual test weight of your grain at its current moisture.

Grain Storage Capacity Calculator

Whether you are reporting inventory, sizing a sale, or insuring stored crop, you need to turn bin and pile dimensions into bushels and tonnes. This calculator handles round bins, rectangular flat storage, and conical piles, converting volume to bushels with the standard factor and to tonnes using grain test weight.

How it works

Each shape gives a volume in cubic feet, which converts to bushels and then to weight:

round bin   = π × radius² × depth   (+ optional cone: (1/3)π r² peak)
flat store  = length × width × depth
cone pile   = (1/3) × π × radius² × peak height
bushels     = cubic feet / 1.2445
tonnes      = bushels × test weight (lb/bu) / 2204.62

The 1.2445 cubic-feet-per-bushel factor is the industry standard for free-flowing dry grain, and test weight (56 lb/bu corn, 60 lb/bu wheat and soybeans) sets the conversion from volume to mass.

Example and tips

A round bin 18 ft in diameter filled to 20 ft of corn holds π × 9² × 20 = 5,089 cubic feet, about 4,090 bushels, and at 56 lb/bu roughly 104 tonnes. For a peaked fill, add the roof cone. For free-standing piles, if you cannot measure the peak, estimate it from the angle of repose (about 23 degrees for corn) — the tool can do this from the base diameter. Always confirm tonnage with a scale where money changes hands.