Grain bin calculator
Enter the inside diameter of the bin and the depth of grain at the wall. If the grain is heaped, add the height of the peak above the wall line. The test weight turns volume into weight: about 56 lb per bushel for corn and 60 for wheat or soybeans.
Runs in your browser: nothing you enter is sent anywhere.
How to use
- Choose US or metric units and enter the inside diameter of the bin.
- Enter the grain depth at the wall (the eave line for a full bin) and, for a heaped load, the height of the peak above it.
- Enter the test weight of the grain and read the capacity and weight.
How it works
- base area = π × diameter² ÷ 4;
- volume = area × depth + area × peak height ÷ 3 (a cylinder and a cone);
- US bushels = cubic feet ÷ 1.2445 (a US bushel is 2,150.42 cubic inches);
- weight = bushels × test weight (lb/bu), or volume × bulk density (kg/hl × 10 = kg/m³).
Example
A 30 ft bin with 20 ft of corn, level, at 56 lb per bushel:
- π × 15² × 20 = 14,137 ft³;
- 14,137 ÷ 1.2445 = 11,360 bushels;
- 11,360 × 56 = 636,167 lb = 318.1 short tons (288.6 t).
Heaped 8 ft above the wall, the cone adds 1,885 ft³: 12,875 bushels. In metric, a 9 m bin 6 m deep holds 381.7 m³, about 274.8 t of grain at 72 kg/hl.
Tips and common mistakes
- Use the inside diameter, not the outside, and measure grain depth from the floor, not from the ground.
- Subtract the space taken by an unloading hopper or a raised floor plenum if you need a close figure.
- Test weight changes with moisture and quality; use the figure from your elevator ticket or scale.
Frequently asked questions
How many bushels are in a grain bin?
Work out the volume in cubic feet and divide by 1.2445, the size of a US bushel (or multiply by 0.8036). A 30 ft bin filled 20 ft deep holds π × 15² × 20 = 14,137 ft³, about 11,360 bushels.
How do I account for a peaked load?
Grain heaped above the wall forms a cone. Its volume is one third of a cylinder with the same base and height, and the calculator adds it when you enter the peak height.
Do bushels here mean volume or weight?
Volume bushels, the space the grain takes. Grain is traded in weight bushels (56 lb of corn, 60 lb of wheat or soybeans); at the standard test weight the two match. Lighter grain fills the same space with fewer weight bushels.
Is grain packed tighter in a big bin?
Yes. Grain compresses under its own weight, so a tall bin holds a few per cent more than the plain volume shows. The calculator does not add this packing factor.