Silo Capacity Calculator
This silo capacity calculator works out the volume and tonnage of a round silo with a flat floor or a cone hopper. Enter the diameter, the straight wall height, the hopper angle, and the stored material, and the silo capacity calculator returns the storage volume in cubic meters and cubic feet, the capacity in metric tons and US tons, and the volume in bushels.
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What the silo capacity calculator does
A silo stores bulk material such as grain, cement, fly ash, or plastic pellets. Its capacity depends on two things: the volume of the cylinder and the hopper, and the bulk density of the material, which is how many tons fill one cubic meter. The silo capacity calculator adds the cylinder volume to the cone hopper volume, applies your fill level, and multiplies by the bulk density to give the tonnage.
Silo capacity formula
The cylinder and the cone hopper are calculated separately:
R is the silo radius, r the outlet radius, H the straight wall height, and α the hopper angle from horizontal. The capacity is the total volume times the fill level times the bulk density. Bushels here are a volume measure, 1.2445 ft³ each, the way grain bin capacity is usually quoted.
Grain silo capacity example
A wheat silo is 6 m across with a 10 m straight wall and a 60 degree cone hopper ending in a 0.3 m outlet:
That is 285.2 US tons or 9,413 bushels of volume. Filled with cement at 1.4 t/m³, the same silo would hold about 464 t.
How to use the silo volume calculator
Choose meters or feet, then enter the inside diameter and the height of the straight wall. For a hopper bottom, enter the cone angle measured from horizontal, usually 45 to 60 degrees, and the outlet diameter. Pick the stored material, or choose a custom density and enter the bulk density of your product. Set the fill level, which is 100% for a full silo. Press Calculate.
Reading the silo tonnage result
The capacity assumes the material fills the silo level to the top of the straight wall. In practice, grain forms a cone on top at its angle of repose, adding a little volume, while a level sensor or the roof shape may stop filling earlier. Bulk density changes with moisture and compaction, so treat the tonnage as an estimate and use your own measured density for contracts and structural loads.
When to use a silo calculator
- Finding the grain silo capacity of a farm bin before harvest
- Checking cement silo capacity at a concrete batching plant
- Estimating how many truck loads fill or empty a silo
- Planning a new silo size for a target tonnage
- Converting silo volume to tons for stock control
Common silo calculator mistakes
- Using outside diameter. Enter the inside diameter of the bin.
- Forgetting the hopper. A cone can add 15% or more to the volume.
- One density for every product. Wheat and barley differ by over 20%.
- Measuring the angle from vertical. Enter the hopper angle from horizontal.
Tips for silo capacity estimates
- Weigh a known volume of your material to get its real bulk density.
- Use a fill level below 100% if the roof or sensors stop filling early.
- Keep a record of tonnage in and out to calibrate the estimate.
Hopper volume and the effect of the cone angle
A steeper hopper empties more reliably but is taller and holds more material in the cone. For a 6 m silo, a 45 degree hopper is 2.85 m deep, while a 60 degree hopper is 4.94 m deep and adds about 1.7 times the volume. Cement and fly ash often need 60 degrees or more to flow, while free-flowing grain can use flatter cones. The cone itself is a frustum, which you can check shape by shape with the volume calculator.
Silo capacity in tons versus usable capacity
The capacity in tons is a gross figure. Some material stays in the hopper after discharge, aeration and moisture change the density, and the structural design of the silo may limit the load to less than the volume allows. For liquids such as molasses or oil, use the tank volume calculator, since liquids fill level. When you plan deliveries, divide the tonnage by the legal payload of your trucks, which the truck load calculator helps with for palletized goods.
Silo capacity per meter of wall height
| Diameter | Volume per m | Wheat (0.78 t/m³) | Corn (0.72 t/m³) | Cement (1.4 t/m³) |
|---|---|---|---|---|
| 3 m | 7.07 m³ | 5.51 t | 5.09 t | 9.90 t |
| 4 m | 12.57 m³ | 9.80 t | 9.05 t | 17.60 t |
| 5 m | 19.63 m³ | 15.31 t | 14.13 t | 27.48 t |
| 6 m | 28.27 m³ | 22.05 t | 20.35 t | 39.58 t |
| 8 m | 50.27 m³ | 39.21 t | 36.19 t | 70.38 t |
| 10 m | 78.54 m³ | 61.26 t | 56.55 t | 109.96 t |
Bulk density of common silo materials
| Material | Bulk density |
|---|---|
| Wheat | 0.78 t/m³ |
| Corn (maize) | 0.72 t/m³ |
| Barley | 0.62 t/m³ |
| Soybeans | 0.75 t/m³ |
| Cement | 1.4 t/m³ |
| Fly ash | 0.9 t/m³ |
| Dry sand | 1.6 t/m³ |
| Wood pellets | 0.65 t/m³ |
Silo Capacity Calculator FAQ
How do you calculate silo capacity?
Add the cylinder volume, π × R² × H, to the hopper volume, then multiply by the bulk density of the material to get tons.
How many tons does a 6 m silo hold?
A 6 m silo with a 10 m wall and a 60 degree hopper holds 331.7 m³, about 259 t of wheat or 464 t of cement.
What is the bulk density of cement in a silo?
Stored cement is usually taken as about 1.4 t/m³; freshly aerated cement can be lighter, near 1.1 to 1.2 t/m³.
How do I convert silo volume to bushels?
Divide the volume in cubic feet by 1.2445, or the volume in cubic meters by 0.03524.