How it works
A round bin is a cylinder, so the volume of grain below the peak is the floor area times the depth. The heaped top is a cone with the same base, whose volume is one third of base area times the peak height. Add the two, then convert cubic feet to bushels.
A US bushel is defined by NIST as 2,150.42 cubic inches, which is about 1.2445 cubic feet, so multiply cubic feet by 0.8036. Weight uses the standard bushel weight for each crop.
Worked example
A 27 ft diameter bin filled 20 ft deep at the wall with a 4 ft peak of corn:
- Floor area = π ÷ 4 × 27² = 572.6 ft²
- Level volume = 572.6 × 20 ft = 11,451 ft³
- Peak volume = 572.6 × 4 ft ÷ 3 = 763 ft³
- Bushels = 12,215 ft³ ÷ 1.2445 ft³/bu = 9,815 bu
- Weight = 9,815 bu × 56 lb ÷ 2,000 = 274.8 tons
| Input | Value |
|---|---|
| Bin diameter | 27 ft |
| Depth of grain at the wall | 20 ft |
| Peak height above the level fill | 4 ft |
| Crop | Corn (shelled), 56 lb/bu |
| Result | Value |
|---|---|
| Capacity with peak | 9,815 bushels |
| Capacity, level fill | 9,202 bushels |
| Bushels in the peak | 613 bushels |
| Total volume | 12,215 ft³ |
| Weight at standard test weight | 274.8 tons |
| Bushels per foot of depth | 460.1 bu/ft |
Standard bushel weights used
| Crop | Pounds per bushel |
|---|---|
| Corn (shelled) | 56 |
| Soybeans | 60 |
| Wheat | 60 |
| Oats | 32 |
| Barley | 48 |
Show the standard bushel weights used table
| Crop | Pounds per bushel |
|---|---|
| Corn (shelled) | 56 |
| Soybeans | 60 |
| Wheat | 60 |
| Oats | 32 |
| Barley | 48 |
Assumptions and limits
- Round bin with a flat floor. Hopper bottoms, aeration ducts, and sump wells add or remove volume.
- The peak is a simple cone and you supply its height. It varies with the crop, moisture, and how it is loaded.
- Bushels are volume bushels. Grain packs under its own weight, so deep bins can hold more, and test weight varies with moisture.
Common questions
How many bushels are in a 27 ft grain bin?
Each foot of depth holds about 460 bushels, so 20 ft holds about 9,200 bushels before the peak.
How many cubic feet in a bushel?
A US bushel is 2,150.42 cubic inches, about 1.2445 cubic feet.
Why does my elevator’s number differ?
Elevators measure by weight and test weight. Grain packs, moisture changes the weight, and the peak shape varies.
Is it safe to enter a grain bin?
Flowing or bridged grain is a serious entrapment hazard. Follow OSHA and your local grain-handling safety practices; this tool does not address safety.
Sources
- NIST Handbook 44 Appendix C: 1 bushel = 2,150.42 cubic inches.
- Standard bushel weights: corn 56 lb; soybeans and wheat 60 lb; oats 32 lb; barley 48 lb (USDA grain standards, OSU Extension).
- Read them: NIST Handbook 44, Appendix C · OSU Extension: Bushels, test weights, and calculations
Updated 2026-09-30