How many bushels are in a grain bin?

Bushels = π × (diameter ÷ 2)² × grain depth ÷ 1.2445. A 30 ft bin filled level to 24 ft holds π × 15² × 24 = 16,965 ft³ ÷ 1.2445 = 13,632 bushels. A full peak of corn adds a cone of about 5.6 ft (at a 20.4° angle of repose), or roughly 1,060 bushels more.

What bushel conversion is used?

The US (Winchester) bushel of 2,150.42 cubic inches = 1.2445 cubic feet = 0.035239 m³. This is a volume bushel; grain trade uses weight bushels (for example 56 lb of corn), which the calculator reports separately as market bushels.

How do I calculate the grain peak in a bin?

A centre-filled bin forms a cone at the grain's angle of repose θ. Peak height = radius × tan θ and peak volume = π r² × height ÷ 3, i.e. one third of a cylinder with the same height. In a 30 ft corn bin with θ = 20.4°, the peak is 15 × tan 20.4° = 5.58 ft high.

What angle of repose should I use?

Measured piling angles in 182 farm and commercial bins (University of Kentucky / USDA-ARS) had medians of 20.4° for corn, 23.9° for soybeans, 22.2° for hard red winter wheat, 24.6° for sorghum, 21.0° for barley and 25.7° for oats; corn ranged from 15.7° to 30.2°. If you can, measure your own peak height and use that instead.

What is test weight and how does it change the bushels?

Test weight is the weight of one volume bushel of your grain. The standard is 56 lb/bu for corn and 60 lb/bu for soybeans and wheat, but light corn may test 52–54 lb/bu. The bin holds the same volume, but weight = volume bushels × test weight, and market bushels = weight ÷ standard weight, so light grain means fewer market bushels.

What is the pack factor?

Grain compacts under the weight of the grain above it, so a deep bin holds more mass than its geometric volume suggests. The pack factor is that extra percentage. It rises with grain depth and moisture and differs by crop; inventory programmes use methods such as USDA RMA, FSA or the ASABE EP413 (WPACKING) model. Leave it at 0% for pure geometric capacity, or use the figure from your bin chart.

Should I use the inside or outside diameter?

The inside diameter. Measure across the bin at floor level, wall to wall, or use the manufacturer's nominal diameter.

How do I estimate a grain pile on the ground?

For a conical pile, measure the base diameter: volume = π r² h ÷ 3 with h = r × tan(angle of repose). For an elongated (ridge) pile, measure length and width: the two ends form one cone and the middle is a triangular prism, so volume = π r² h ÷ 3 + (length − width) × width × h ÷ 2.

Grain Storage Calculator

Enter bin diameter and grain depth (or building / pile size) to get bushels, cubic feet, cubic metres and weight. Includes the grain peak at the crop's angle of repose, hopper bottoms, coned-down bins, flat storage, conical and elongated piles, test weight and an optional pack factor. 1 bushel = 1.2445 ft³.

Storage & Grain

Storage shape

Units

Inside diameter (ft)

Grain depth at wall (ft)

Use the eave height when the bin is full to the eave.

Grain surface

Hopper angle (°)

Crop

Angle of repose (°)

Test weight (lb/bu)

Pack factor (%)

Standard weight (lb/bu)

Bushels (volume)

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1 bu = 1.2445 ft³

Cubic Feet

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ft³ (geometric)

Cubic Meters

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m³ (geometric)

Volume breakdown

Weight

Bushels incl. pack factor

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Pounds

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Short tons (US)

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Metric tonnes

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Market bushels (÷ standard weight)

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Round grain bin capacity chart (bushels, level fill)

π × (D/2)² × eave height ÷ 1.2445 ft³/bu. No peak, no hopper, no pack factor. "Per ft" = bushels per foot of grain depth.

Diameter	Per ft	16 ft	20 ft	24 ft	28 ft	32 ft
18 ft	204	3,272	4,089	4,907	5,725	6,543
21 ft	278	4,453	5,566	6,680	7,793	8,906
24 ft	364	5,816	7,270	8,724	10,178	11,632
27 ft	460	7,361	9,201	11,042	12,882	14,722
30 ft	568	9,088	11,360	13,632	15,904	18,176
33 ft	687	10,996	13,745	16,494	19,243	21,992
36 ft	818	13,086	16,358	19,630	22,901	26,173
42 ft	1,113	17,812	22,265	26,718	31,171	35,624
48 ft	1,454	23,265	29,081	34,897	40,713	46,529
54 ft	1,840	29,444	36,805	44,167	51,528	58,889
60 ft	2,272	36,351	45,439	54,527	63,614	72,702

Crop constants used

Crop	Standard weight	Piling angle (median)	Peak of a 30 ft bin
Corn	56 lb/bu	20.4°	5.6 ft · 1,056 bu
Soybeans	60 lb/bu	23.9°	6.6 ft · 1,258 bu
Wheat (HRW)	60 lb/bu	22.2°	6.1 ft · 1,159 bu
Grain sorghum	56 lb/bu	24.6°	6.9 ft · 1,300 bu
Barley	48 lb/bu	21.0°	5.8 ft · 1,090 bu
Oats	32 lb/bu	25.7°	7.2 ft · 1,367 bu

Standard bushel weights: USDA. Piling angles: medians measured in 182 bins (University of Kentucky / USDA-ARS); individual bins vary by several degrees.

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Summary

The grain storage calculator turns storage dimensions into bushels. A round bin is a cylinder (π r² × grain depth at the wall) plus a cone for the peak (π r² × h ÷ 3, with h = r × tan of the angle of repose) or minus a cone when the bin has been cored down, plus a hopper cone if it has a hopper bottom. Flat storage adds a hip-roof shaped peak; outdoor piles are a cone or a cone split by a ridge. Volume is converted with the US bushel of 1.2445 ft³. Weight uses the measured test weight in lb/bu, and "market bushels" divide that weight by the crop's standard bushel weight (56 lb for corn, 60 lb for soybeans and wheat). An optional pack factor adds the extra grain that compaction squeezes into deep bins.

How it works

Choose the storage shape: round bin, flat storage building, conical pile or elongated pile, and feet or metres.
Enter the inside diameter (or length and width) and the grain depth at the wall — the eave height if the bin is full to the eave.
Pick the grain surface: level, peaked (cone at the angle of repose) or coned down (inverted cone after unloading); add the hopper angle for hopper-bottom bins.
Select the crop to load its angle of repose and standard bushel weight, then enter your measured test weight and an optional pack factor.
Read bushels, cubic feet, cubic metres, the volume breakdown and the weight in pounds, short tons, tonnes and market bushels.

Use cases

Estimate whether an existing bin can hold a full field harvest before grain is delivered.
Measure grain inventory in a partly filled or cored-down bin for marketing or loan paperwork.
Estimate bushels in an outdoor ground pile or a flat storage building.
Compare capacity options when shopping for a new grain bin by trying different diameters and eave heights.
Convert bin volume to weight using the actual test weight of this year's crop.
Calculate how many bins are needed to store a given amount of grain at harvest time.

Frequently Asked Questions

Last updated: 2026-10-10 · Reviewed by Nham Vu