GRAIN BIN CALCULATOR
| ⌀ | 18 ft | 21 ft | 24 ft | 27 ft |
|---|---|---|---|---|
| 18 ft | 3,681 | 4,294 | 4,908 | 5,521 |
| 24 ft | 6,544 | 7,634 | 8,725 | 9,816 |
| 30 ft | 10,225 | 11,929 | 13,633 | 15,337 |
| 36 ft | 14,723 | 17,177 | 19,631 | 22,085 |
| 48 ft | 26,175 | 30,537 | 34,900 | 39,262 |
Calculated Capacity & Value
Cylinder = π × r² × hPeaked cone = ⅓ × π × r² × (r × tan 25°)Hopper cone = ⅓ × π × r² × (r × tan θ)Shrink % = (Moist In − Std) × 1.3Dry Bu = Wet Bu × (1 − Shrink%)Drying Cost = Pts to dry × $/pt × Dry BuAngle 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 13,600 bu level-fill (1 bu = 1.244 ft³). Add a peaked cone surface for ~14,950 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’s cone stores grain below the cylinder, so for the same wall height it actually holds a bit more than a flat floor — the calculator adds that cone volume. Hoppers are chosen for gravity unloading (no sweep auger), usually at smaller diameters.
- 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.