Silo Storage Capacity Calculator

Estimate cylindrical silo capacity from filled volume and bulk density

A silo capacity calculator converts internal dimensions into cylindrical volume and multiplies that volume by bulk density to estimate stored tonnes. A usable-fill percentage can reduce the geometric volume for headspace or other operational allowance.

Bulk density is the critical material input. Silage, grain and other stored feeds can have very different densities, and density can vary with moisture, packing, particle size and depth. A precise tape measurement cannot compensate for an inappropriate density assumption.

How the calculation works

Volume is reduced by usable-fill percentage and multiplied by user-supplied bulk density. The tool calculates π × radius² × filled height, multiplies cubic metres by kilograms per cubic metre and the usable-fill fraction, then divides by 1,000 to convert kilograms to tonnes.

Diameter and filled height are metres, bulk density is kg/m³ and capacity is metric tonnes. Use internal dimensions and a density expressed on the same as-stored basis as the material being estimated.

What each calculator input means

Internal diameter

Use internal silo diameter rather than outside wall measurement. Verify whether liners, internal structures or taper materially reduce usable cross-section. The field is entered in m.

Filled height

Enter actual filled material height, not total structure height. Maintain required headspace and do not assume the silo should be filled to its physical top. The field is entered in m.

Bulk density

Use a bulk-density estimate appropriate for the stored material, moisture and packing. For silage, density can vary substantially with packing management and depth. The field is entered in kg/m³.

Usable fill

Use the percentage of the calculated cylinder that is intentionally available for product. Headspace, floor geometry or operating reserve can justify a value below 100%. The field is entered in %.

Density uncertainty often controls tonnage accuracy

Capacity in cubic metres is primarily geometry; capacity in tonnes requires density. If actual bulk density is 10% different from the entered value, the tonnage estimate changes by roughly the same percentage.

Use measured load weights and known filled volume to calibrate density for your system when possible. Generic density tables are useful for screening but should be treated as approximations.

Storage safety is not a capacity calculation

Knowing that material could geometrically fit does not establish that a silo can safely carry the load or that filling and unloading are safe. Structural condition, pressure, unloading equipment and gas or engulfment hazards require separate controls.

Follow manufacturer limits and established silo safety procedures. Never use a capacity estimate to justify exceeding structural or operating recommendations.

Worked example

A 6 m diameter silo filled 15 m with 750 kg/m³ material at 95% usable fill holds about 302 tonnes.

A 6 m diameter cylinder filled to 15 m has about 424 m³ of geometric volume. At 750 kg/m³ and 95% usable fill, estimated stored mass is approximately 302 tonnes.

Use tonnage estimates for feed and storage planning, not structural approval

Compare expected harvest or feed inventory with usable storage and material density. If a silo is consistently holding more or less mass than predicted, use scale records to refine the density assumption.

For silage, storage capacity should be coordinated with feed-out rate and spoilage management. Extra theoretical tonnage is not beneficial if face management, unloading safety or forage quality suffers.

• Estimate stored tonnes from silo dimensions and material density.
• Compare expected crop tonnage with available silo volume.
• Test how density or usable fill changes storage capacity.
• Cross-check feed inventory against known delivered weights.

Common mistakes that can distort the result

• Using outside diameter instead of internal diameter.
• Using total structure height instead of filled material height.
• Applying a generic density to material with very different moisture or packing.
• Assuming 100% geometric fill is operationally usable.
• Treating calculated capacity as permission to exceed structural limits.

Limitations and responsible use

The model assumes a simple vertical cylinder with uniform density. It does not account for conical sections, variable compaction, bridging, wall loads, structural condition or material settlement.

Use manufacturer information, measured weights and professional engineering where structural capacity is uncertain. Stored-feed and silo hazards require appropriate safety procedures independent of the calculation.

For feed budgeting, compare the calculated tonnes with actual delivered or harvested weights and the amount removed over time. That comparison can refine the working density used for future estimates and can also reveal unexpected storage loss, spoilage or measurement assumptions that need attention. Keep those checks by crop, moisture range and storage method so future density assumptions become more representative of the material actually handled on the farm.

For the next step in the same planning workflow, compare the result with Grain Bin Capacity Calculator, Cattle Feed Requirement Calculator and Grain Moisture Adjustment Calculator. Using related calculations together can expose an assumption that is easy to miss when a single number is viewed on its own.