Grain Bin Volume Calculator
Calculate how many bushels, cubic feet, and metric tonnes your grain bin holds. Supports round and square bins with flat or peak roofs. Select your grain type for accurate weight estimates.
What is a grain bin volume calculator?
A grain bin volume calculator estimates how many bushels, cubic feet, or metric tonnes of grain a storage bin can hold. You enter the bin's dimensions — diameter and height for round bins, or length, width, and height for square bins — plus the roof style and grain type. The calculator applies the right geometric formula, accounts for a standard packing factor, and converts the result into the units farmers and grain handlers use every day.
Getting storage capacity right matters for harvest planning, insurance, marketing, and logistics. Knowing your bin holds 8,500 bushels instead of estimating 10,000 prevents overfilling, spoilage, and safety hazards. It also helps you match your bin inventory against contracts and delivery schedules before you cut the crop.
This tool is part of the CalcMora Converters section. Farmers and contractors who work with both on-farm storage and structural projects may also find the rafter length calculator helpful for bin roof and outbuilding work. For pipeline and irrigation planning on the same property, the pipe volume calculator handles water flow sizing. And when it comes time to price grain bin installation or construction jobs, the markup to margin calculator helps you set a profitable selling price from your material and labour costs.
Grain bin volume formulas
A round grain bin is a cylinder with a cone on top. The capacity calculation adds the cylinder volume of the sidewall section to the cone volume of the roof, applies a packing factor, then converts cubic feet to bushels using the grain's known bulk density.
Cylinder (sidewall)
V = π × (d ÷ 2)² × h
Where d is diameter in feet and h is sidewall height. Result is in cubic feet.
Cone (peak roof)
V = (1 ÷ 3) × π × (d ÷ 2)² × peak height
The roof cone adds meaningful volume on tall-peak bins. Omit this for flat roofs.
Usable volume
Usable ft³ = (cylinder + cone) × packing factor
Standard packing factor is 0.80. Grain never fills every cubic inch of geometric space.
Bushels
Bushels = usable ft³ ÷ ft³ per bushel
One US bushel = 1.2445 cubic feet. Divide usable volume by this to get bushel count.
For square bins, replace the cylinder formula with a rectangular box: V = length × width × height. The roof calculation uses the same cone formula if a peak roof is present.
Grain bushel weights reference
Different grains have different official bushel weights set by USDA standards. These weights determine how cubic feet convert to bushels and how bushels convert to tonnes. The table below shows the standard values this calculator uses.
| Grain | lbs per bushel | kg per bushel | ft³ per bushel | Bushels per tonne |
|---|---|---|---|---|
| Wheat | 60 | 27.22 | 1.2445 | 36.74 |
| Corn | 56 | 25.40 | 1.2445 | 39.37 |
| Soybeans | 60 | 27.22 | 1.2445 | 36.74 |
| Barley | 48 | 21.77 | 1.2445 | 45.93 |
| Oats | 32 | 14.52 | 1.2445 | 68.89 |
| Canola | 50 | 22.68 | 1.2445 | 44.09 |
| Grain Sorghum | 56 | 25.40 | 1.2445 | 39.37 |
| Sunflower | 25 | 11.34 | 1.2445 | 88.18 |
| Flaxseed | 56 | 25.40 | 1.2445 | 39.37 |
| Rye | 56 | 25.40 | 1.2445 | 39.37 |
Common grain bin sizes and estimated wheat capacity
| Diameter (ft) | Sidewall (ft) | Approx. bushels (wheat) | Approx. metric tonnes |
|---|---|---|---|
| 15 | 14 | ~1,600 | ~44 |
| 18 | 16 | ~2,600 | ~71 |
| 21 | 18 | ~4,000 | ~109 |
| 24 | 18 | ~5,200 | ~141 |
| 27 | 20 | ~7,400 | ~201 |
| 30 | 20 | ~8,500 | ~231 |
| 36 | 24 | ~14,800 | ~403 |
| 48 | 28 | ~30,500 | ~830 |
These figures use a 0.80 packing factor and a 4-foot peak roof. Actual capacity varies by bin manufacturer, wall profile, and grain condition. Always use this calculator with your exact bin measurements for the most useful estimate.
Worked examples
Example 1: 30-ft round bin, wheat
A 30-foot diameter bin with a 20-foot sidewall and a 5-foot peak roof holds about 8,700 bushels of wheat at a 0.80 packing factor. That is roughly 237 metric tonnes — useful for pre-harvest logistics planning and crop insurance declarations.
Example 2: 24-ft round bin, canola
Canola has a lower lbs-per-bushel rating than wheat, so the same bin holds more bushels but less weight per bushel. A 24-foot bin with an 18-foot wall holds about 5,200 bushels of canola, weighing roughly 118 metric tonnes — important for transport permit calculations.
Example 3: Square bin, corn
A square bin that is 20 feet long, 20 feet wide, and 16 feet tall with a flat roof holds about 3,670 bushels of corn at a 0.80 packing factor. Square bins are common for on-farm drying setups and temporary storage near harvest equipment.
Example 4: Large commercial bin, soybeans
A 48-foot diameter commercial bin with a 28-foot sidewall and a 6-foot peak holds over 31,000 bushels of soybeans, weighing approximately 844 metric tonnes. Knowing this capacity is essential for scheduling deliveries and managing elevator contracts.
Grain bin volume calculator FAQ
How do I calculate grain bin capacity in bushels?
For a round bin, calculate the volume of a cylinder using V = π × (diameter/2)² × height, then multiply by 0.8 to account for the fact that grain does not fill a bin to 100% efficiency. Divide the cubic feet result by the cubic feet per bushel for your grain type. Wheat and soybeans are approximately 1.244 cubic feet per bushel, corn is about 1.244 cubic feet per bushel, and canola is slightly different. This calculator handles all those conversions automatically once you select the grain type.
What is the standard grain bin size?
Round grain bins are typically described by diameter and height. Common farm bin diameters run from 15 feet to 48 feet. A 30-foot diameter bin with a 20-foot sidewall is one of the most common sizes on mid-sized farms and holds roughly 7,800 to 8,500 bushels of wheat depending on roof style and peak height. Commercial bins can exceed 105 feet in diameter.
How do I measure my grain bin diameter?
Measure across the widest point of the bin from the outside edge to the outside edge, then subtract the wall thickness (usually 3 to 5 inches per side for corrugated steel bins) to get the inner diameter. For most farm planning purposes, the outside diameter is close enough. This calculator uses the diameter you enter directly in its formula.
Does roof style affect grain bin capacity?
Yes. A peaked roof adds extra storage volume above the sidewall height. A flat or standard roof adds very little. This calculator lets you choose between peak roof and flat roof, and for peak roofs you can enter the peak height to get a more accurate total capacity. The roof cone volume is added to the cylinder volume of the sidewall section.
How many bushels fit in a 30-foot bin?
A 30-foot diameter round bin with a 20-foot sidewall holds approximately 7,700 to 8,500 bushels of wheat, depending on roof type and peak height. For corn, the number is similar since corn and wheat share nearly the same bushel volume. For canola or flaxseed, which are heavier per cubic foot, the bushel count changes because the bushel weight differs. Use this calculator and select your grain type for the most accurate estimate.
What is the packing factor for grain bins?
Grain does not settle into every cubic inch of space uniformly. A common packing factor used in planning is 0.8 — meaning only 80% of the geometric volume is usable for grain storage. Some grain types pack more tightly. This calculator applies a standard 0.8 packing factor to the cylinder volume to give a practical capacity estimate rather than a theoretical maximum.
Can I calculate grain weight in tonnes from this calculator?
Yes. Once the calculator knows the bushel count and your grain type, it multiplies by the weight per bushel and converts to metric tonnes. For example, wheat is approximately 60 pounds per bushel, so 10,000 bushels of wheat weighs about 272 metric tonnes. The calculator shows both imperial and metric weight outputs.
This tool is for educational purposes only. Always verify important results with a qualified professional.
