Grain Bin Calculator

How to Use the Grain Bin Calculator

Using this grain bin calculator is straightforward. Follow these steps to determine the storage capacity of your bin:

1. Select your bin shape -- choose Round/Cylindrical for standard round bins, or Rectangular for flat storage buildings and rectangular bins.
2. Enter your bin dimensions -- for round bins, enter the diameter (the radius is calculated automatically). For rectangular bins, enter the length and width.
3. Enter the grain height -- this is how high the grain sits inside the bin, not the total bin wall height.
4. Toggle peaked/cone top -- if your grain is peaked above the sidewall, turn this on and enter the peak height.
5. Toggle hopper bottom (round bins only) -- if your bin has a hopper (cone-shaped) bottom, enable this and enter the hopper height.
6. Select your grain type -- choose the type of grain you are storing. This determines the weight per bushel used in calculations. Select "Custom" if your grain type is not listed.
7. Click "Calculate Grain Bin Capacity" -- the calculator will display the total volume, bushel capacity, grain weight, tonnage, and floor area. A diagram of your bin will also be displayed.

What is a Grain Bin?

A grain bin (also called a grain silo) is a storage structure used to store harvested grain until it can be sold, processed, or used as feed. Grain bins are essential infrastructure for modern farming operations, allowing farmers to:

• Store grain to sell at optimal market prices
• Protect grain from weather, pests, and spoilage
• Maintain grain quality through temperature and moisture control
• Buffer supply chain disruptions

Types of Grain Bins

Round (Cylindrical) Bins

• Most common type in modern agriculture
• Made of corrugated steel panels bolted together
• Diameters typically range from 15 to 105 feet
• Heights from 15 to 50+ feet
• Capacities from 1,500 to over 1,000,000 bushels
• Superior structural strength (no corners for stress concentration)
• Easier to unload (gravity flow to center)

Flat-Bottom Bins

• Floor is a flat concrete pad
• More affordable to construct
• Require mechanical unloading (augers, conveyors, sweep systems)
• Better for long-term storage
• Common for large commercial operations

Hopper-Bottom Bins

• Cone-shaped bottom allows gravity unloading
• No sweep equipment needed
• More expensive than flat-bottom
• Limited in maximum size
• Ideal for frequently loaded/unloaded operations
• Common for seed, feed, and specialty grains

How to Calculate Grain Bin Capacity

Cylindrical Bin Formula

The volume of a cylindrical grain bin is calculated using:

Volume (cu ft) = π × r² × h

Bushels = Volume × 0.7786

Where:

• r = radius in feet (diameter / 2)
• h = height of grain in feet
• 0.7786 = conversion factor from cubic feet to bushels

Adding Peaked Grain (Cone on Top)

When grain is peaked in a cone shape above the sidewall:

Volume of cone = (1/3) × π × r² × peak_height

Add this volume to the cylinder volume, then convert the total to bushels.

Example Calculation

Bin diameter: 30 feet, Grain height: 20 feet, Peak height: 3 feet

• Radius = 15 feet
• Cylinder volume = π × 15² × 20 = 14,137 cu ft
• Peak volume = (1/3) × π × 15² × 3 = 707 cu ft
• Total volume = 14,844 cu ft
• Bushels = 14,844 × 0.7786 = 11,558 bushels
• At 56 lbs/bu (corn): 647,248 lbs = 323.6 tons

Bushel Weight by Grain Type

Grain Storage Best Practices

• Moisture control: Store grain at 13-15% moisture for corn, 13% for wheat/soybeans.
• Temperature monitoring: Check regularly and aerate to cool grain down.
• Pest management: Inspect for insects monthly.
• Aeration fans: Run during cool nights to reduce temperature.
• Clean bins thoroughly between crop seasons to prevent contamination.
• Level grain surface: Peaked grain has poor airflow in the center.
• Do not overfill: Leave space for aeration and inspection access.

Round vs Flat Bottom Grain Bins

Round Bottom (Hopper)

• Advantages: Gravity unloading, faster turnaround, no sweep needed
• Disadvantages: Higher cost, size limitations, taller structure

Flat Bottom

• Advantages: Lower cost per bushel, larger capacities available
• Disadvantages: Need mechanical unloading equipment, slower to empty

Grain Bin Safety

• Grain entrapment: NEVER enter a bin with flowing grain. Entrapment can occur in seconds.
• Toxic gases: Grain can produce carbon dioxide and nitrogen dioxide during spoilage.
• Falls: Use proper fall protection when working on top of bins.
• Electrical hazards: Ensure proper grounding of all equipment.
• Lock out / tag out: Always disable equipment before entering a bin.

Approximately 30-40 grain bin entrapment cases occur annually in the United States. Safety must always come first.

Frequently Asked Questions