Last updated: June 20, 2026
Grain Bin Calculator
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
The Grain Bin Calculator estimates the storage capacity of a round grain bin in bushels, cubic feet, and tons. The grain forms a cylinder of volume π × r² × h, plus a cone (⅓ × π × r² × p) for the peak when overfilled; dividing the total cubic feet by 1.2445 gives bushels. For example, a 24-foot-diameter bin filled to 18 feet holds π × 12² × 18 = 8,143 cubic feet, about 6,543 bushels, or roughly 183 tons of corn at 56 pounds per bushel. Weight depends on the grain's test weight — corn 56 lb/bu, wheat and soybeans 60 lb/bu. Always use the inside diameter and the actual grain depth.
To find a round grain bin's capacity, square the radius, multiply by pi and the grain height to get cubic feet, then divide by one point two four four five to get bushels. For example, a twenty-four foot bin filled to eighteen feet holds about six thousand five hundred forty-three bushels.
Key Takeaways
- Bin capacity = (π × r² × grain height) ÷ 1.2445, where r is half the diameter
- One US bushel occupies 1.2445 cubic feet of grain
- An overfilled bin adds a cone of grain: ⅓ × π × r² × peak height
- Weight depends on test weight — corn 56 lb/bu, wheat and soybeans 60 lb/bu
- Always use the inside diameter and the actual grain depth, not the wall height
- A 24-ft bin filled to 18 ft holds about 6,543 bushels (≈183 tons of corn)
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
bushels = (π × r² × h + ⅓ × π × r² × p) / 1.2445
Where:
- r=Bin radius (half the diameter)(feet)
- h=Grain height in the cylindrical wall(feet)
- p=Coned peak height above the eave(feet)
- 1.2445=Cubic feet per US bushel(ft³/bu)
Worked Examples
24-foot bin filled level to 18 feet
A common on-farm corn bin, 24 ft in diameter with grain 18 ft deep and no peak.
- 1Find the radius: r = 24 / 2 = 12 ft
- 2Cylinder volume: π × 12² × 18 = 8,143 ft³
- 3Convert to bushels: 8,143 / 1.2445 ≈ 6,543 bu
- 4Weight: 6,543 bu × 56 lb ÷ 2,000 ≈ 183 tons
Same bin with a coned peak
The 24-ft bin is overfilled with a 6-ft grain peak above the eave.
- 1Cylinder volume: π × 12² × 18 = 8,143 ft³
- 2Peak (cone) volume: ⅓ × π × 12² × 6 = 905 ft³
- 3Total: 9,048 ft³ → 9,048 / 1.2445 ≈ 7,270 bu
Large 48-foot wheat bin
A larger bin, 48 ft across, holding wheat 30 ft deep with a level top.
- 1Radius: r = 24 ft
- 2Volume: π × 24² × 30 = 54,287 ft³
- 3Bushels: 54,287 / 1.2445 ≈ 43,621 bu
- 4Weight: 43,621 × 60 ÷ 2,000 ≈ 1,309 tons
Introduction
The Grain Bin Calculator estimates how much grain a round (cylindrical) storage bin holds, in bushels, cubic feet, and tons. Farmers, grain merchandisers, and elevator operators use bin capacity to plan harvest logistics, manage inventory, and price stored grain. The calculator treats the grain as a cylinder — volume = π × r² × h — plus an optional cone for the peak when a bin is overfilled, then converts the volume to bushels (1 bushel = 1.2445 ft³) and to weight using each grain's standard test weight. For related agronomy and storage tools, see our Corn Yield Calculator, Grain Conversion Calculator, and Dry Matter Calculator.
How Grain Bin Capacity Is Calculated
Grain in a round bin forms a cylinder, and when overfilled, a cone-shaped peak on top. The total volume in cubic feet is the cylinder plus the cone, and dividing by 1.2445 ft³ per bushel converts that volume to bushels.
- Step 1:
Find the radius — half the bin diameter
- Step 2:
Cylinder volume = π × r² × grain height
- Step 3:
Peak volume = ⅓ × π × r² × peak height (0 if level)
- Step 4:
Bushels = total cubic feet ÷ 1.2445
- Step 5:
Weight (tons) = bushels × test weight ÷ 2,000
Measure the grain height, not the bin's total wall height — a bin is rarely filled to the very top of the sidewall.
Bushels, Cubic Feet, and Test Weight
A bushel is a unit of volume, not weight: one US bushel occupies 1.2445 cubic feet. The weight of that bushel depends on the grain's density, expressed as test weight in pounds per bushel. The U.S. legal weights are standardized so a bushel of corn is 56 lb while a bushel of wheat or soybeans is 60 lb. See the USDA grain inspection standards for official definitions.
| Grain | Test weight (lb/bu) | Tons per 1,000 bu |
|---|---|---|
| Corn | 56 | 28.0 |
| Wheat | 60 | 30.0 |
| Soybeans | 60 | 30.0 |
| Barley | 48 | 24.0 |
| Oats | 32 | 16.0 |
| Grain sorghum (milo) | 56 | 28.0 |
| Rye | 56 | 28.0 |
Test weight varies with moisture and grain quality; the values above are the standard legal weights used for trade.
Round Bins vs. Other Shapes
This calculator models a round bin, the most common on-farm shape. Flat (rectangular) storage and hopper-bottom bins use different geometry, so adjust your inputs accordingly when a bin is not a simple upright cylinder.
Round upright bin — cylinder (this calculator)
Overfilled round bin — cylinder plus a cone for the peak
Hopper-bottom bin — add the cone of the hopper below the cylinder
Flat storage — length × width × depth instead of π × r²
Grain piles on the ground — modeled as a cone or wedge
For a hopper bin, estimate the lower cone separately and add it to the cylindrical capacity.
Practical Applications
Knowing bin capacity turns dimensions into decisions. It supports harvest planning, inventory control, drying management, and grain marketing.
Plan how many bins or how much extra storage a harvest will need
Track inventory and reconcile bin readings with scale tickets
Estimate the value of stored grain at the current cash price
Size aeration fans and drying systems to bin volume
Decide when to haul, sell, or move grain between sites
Tips for Accurate Results
Bin estimates are only as good as the measurements and assumptions behind them. A few habits keep your numbers trustworthy.
Use the inside diameter, not the outside of the corrugated wall
Measure the actual grain depth — bins are seldom filled level to the eave
Include the peak for overfilled bins; it can add several hundred bushels
Match the grain type so the weight uses the correct test weight
Remember settling and packing slightly increase real bushels over time
Cross-check the calculated capacity against the bin manufacturer's rated bushel chart when you have it.
Quick Reference Card
Grain Bin Capacity — Quick Reference
Quick reference • Grain Bin Calculator
bushels = (π × r² × h) ÷ 1.2445 · peak adds ⅓ × π × r² × pValid range: 1 bushel = 1.2445 ft³; weight = bushels × test weight ÷ 2,000
Common Values
⚠ Watch Out
- •Use the inside diameter, not the outside of the wall
- •Measure actual grain depth, not the full sidewall height
- •Include the peak for overfilled bins
- •Test weight varies with moisture and grain quality
Pro Tips
- →Doubling the diameter quadruples capacity at the same height
- →Add the lower hopper cone for hopper-bottom bins
- →Cross-check against the manufacturer's bushel chart
- →Reconcile calculated bushels with scale tickets
FAQs
How do you calculate the capacity of a round grain bin?
Find the radius (half the diameter), compute the cylinder volume as π × r² × grain height in cubic feet, then divide by 1.2445 to convert to bushels. For example, a 24-foot bin filled to 18 feet holds π × 12² × 18 = 8,143 cubic feet, which is about 6,543 bushels. If the bin is overfilled, add the cone-shaped peak volume (⅓ × π × r² × peak height) before converting.
How many cubic feet are in a bushel?
One US bushel occupies 1.2445 cubic feet. This is a volume conversion, so it applies to any grain regardless of weight. To convert a bin's cubic-foot volume to bushels, divide by 1.2445; to go the other way, multiply bushels by 1.2445.
How much does a bushel of grain weigh?
It depends on the grain's standard test weight: a bushel of corn weighs 56 pounds, wheat and soybeans 60 pounds, barley 48 pounds, and oats 32 pounds. These legal weights are used for trade. The calculator multiplies bushels by the test weight of the grain you select to estimate the stored weight in tons.
Does the peak on top of an overfilled bin matter?
Yes. When a bin is filled past the eave, the grain forms a cone whose volume is ⅓ × π × r² × peak height. On a wide bin this can add several hundred bushels, so include the peak height for an accurate estimate. For a level fill, leave the peak height at zero.
Should I use the inside or outside diameter?
Use the inside diameter. The corrugated wall and stiffeners mean the outside diameter is slightly larger than the space the grain actually occupies. Using the outside diameter overstates capacity, and the error grows with the square of the radius, so it matters more on large bins.
Does grain settling change the capacity?
Slightly. As grain sits, it packs and settles, so a bin can hold a few percent more than a fresh-fill estimate suggests. The calculator uses standard packing assumptions; for inventory reconciliation, compare calculated bushels with scale tickets and adjust with a packing factor if your operation tracks one.
Can I use this calculator for a hopper-bottom bin?
Partly. This tool models the upright cylindrical portion plus an optional top peak. A hopper-bottom bin also has a cone of grain below the cylinder. Estimate that lower cone separately (⅓ × π × r² × hopper height) and add it to the cylindrical capacity for the full total.