How many bushels does a 30-foot grain bin hold?

A 30-foot diameter round bin with a 24-foot eave height holds approximately 11,317 bushels at level fill and standard moisture. Add a peaked cone surface to get roughly 12,700 bushels.

What is the grain shrink formula?

The standard formula is: Shrink % = (Moisture In minus Standard Moisture) times 1.3. For corn at 18% moisture, shrink = (18 - 15.5) x 1.3 = 3.25%. This accounts for both water removal and handling loss.

What is pack factor in a grain bin?

Pack factor is the additional compaction of grain that occurs as the bin fills and grain settles over time. For corn, a typical pack factor is 0.5 to 1.5%. Leave it at 0 if you want a conservative baseline estimate.

How do hopper-bottom bins differ from flat-floor bins?

Hopper-bottom bins have an inverted cone at the bottom that drains grain by gravity. Because the cone takes up space that a flat floor would not, a hopper-bottom bin holds slightly fewer bushels than a flat-floor bin of the same diameter and wall height.

How is drying cost calculated for corn?

Drying cost is typically quoted in dollars per point (1 percentage point of moisture) per bushel. A common range is $0.03 to $0.05 per point per bushel. To dry corn from 18% to 15.5% costs 2.5 points, so roughly $0.09 per bushel at $0.035/point.

🌾 GRAIN BIN CALCULATOR

Crop Type

Bin Shape

● Round ▽ Hopper ▬ Rectangular

Diameter (ft)

Eave Height (ft)

Grain Surface

▲ Peaked ▬ Level ▼ Draw

Grain Depth 24.0 ft • 100%

Market Price

Price ($/bu) ↗ cash bids

Moisture, Drying & Packing

Moisture In (%)

Target Moisture (%)

Drying Cost ($/pt/bu)

Pack Factor (%) ⓘ

Pack factor: industry norm 0.5–1.5% for corn after settling. Leave at 0 for conservative estimate.

Cross-Section View

Common Round Bin Capacities (Level Fill)

⌀	18 ft	21 ft	24 ft	27 ft
18 ft	3,050	3,561	4,072	4,583
24 ft	5,432	6,338	7,244	8,150
30 ft	8,488	9,903	11,317	12,732
36 ft	12,222	14,259	16,297	18,334
48 ft	21,728	25,350	28,971	32,593

              Bushels at standard moisture, no pack. Rows = diameter, cols = eave height.
            

Calculated Capacity & Value

Bushels & Weight

Total Bushels--

Weight--

Cylinder Volume--

Surface Adj.--

Total Volume--

Moisture Shrink

Shrink Factor--

Dry Bushels--

Bushels Lost--

Gross Value (wet bu)--

Value After Shrink--

Drying Cost--

Net Value--

Safe Storage Moisture Targets

Corn — 1 year

14%

Corn — long term

13%

Soybeans

13%

Wheat

13.5%

Formulas Used
Cylinder = π × r² × h
Peaked cone = ⅓ × π × r² × (r × tan 25°)
Hopper cone = ⅓ × π × r² × (r × tan θ)
Shrink % = (Moist In − Std) × 1.3
Dry Bu = Wet Bu × (1 − Shrink%)
Drying Cost = Pts to dry × $/pt × Dry Bu
Angle of repose ≈ 25° for peaked grain (tan 25° ≈ 0.466). Pack factor accounts for grain settling over time.

How to Use This Grain Bin Calculator

Enter your bin diameter and eave height (or length, width, and depth for rectangular storage), choose your crop, and the calculator instantly shows total bushel capacity, weight, and — if you enter a market price — estimated net value after moisture shrink and drying costs. The depth slider lets you model a partially filled bin. Use the Hopper option for bins with an inverted-cone floor; the calculator automatically adds the hopper cone volume to your total.

Understanding Moisture Shrink

Grain delivered above standard moisture loses weight — and value — during drying. The industry standard shrink formula is (Moisture In − Standard Moisture) × 1.3. The 1.3 multiplier covers both the water removed and a small handling loss allowance. Corn at 18% moisture heading into a 15.5%-standard market shrinks 3.25%, costing roughly 85 to 100 bushels on a 3,000-bushel truckload. For a complete picture, enter a drying cost (typically $0.03–$0.05 per point per bushel) to see your true net value after all shrink and drying charges. Check local cash bids →

Common Questions

How many bushels in a 30-foot bin?: A 30×24 ft round bin holds about 11,317 bu level-fill at standard moisture. Add a peaked cone surface for ~12,700 bu.
What is pack factor?: Grain settles 0.5–1.5% over time as kernels compact. Leave it at 0 for a conservative estimate. Use 1% for a bin that’ll sit all winter.
Hopper bottom vs. flat floor?: A hopper bin holds slightly less than a flat-floor bin of the same wall height because the cone takes space a flat floor would fill solidly.
How do I figure drying cost?: Multiply points to dry × $/pt/bu. Drying from 18% to 15.5% = 2.5 pts. At $0.035/pt: 2.5 × $0.035 = $0.0875/bu.