Why does canola store fewer tonnes than wheat in the same silo?

Canola bulk density is ~650 kg/m3 vs wheat ~780 kg/m3 — about 17% less dense. Silo specs are nearly always based on wheat. Always recalculate canola capacity separately.

How to measure bulk density on farm?

Fill a calibrated 10-litre bucket with grain from 300 mm height (don't shake). Weigh in grams. Divide by 10 to get kg/m3. Quick and accurate.

What grain protectant for long-term storage?

Wheat in sealed silos: diatomaceous earth (DE) at label rate is the most common low-residue option. Canola: hermetic (oxygen-limiting) storage is increasingly preferred as DE is less effective on round canola seed. Always check current registered products.

Grain Storage Volume — Free Agriculture Calculator

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New silo order is being finalised. Before the fabricator quotes you need to confirm cubic metre capacity and expected tonnes of canola at site bulk density — to know if a second bin is needed before harvest.

Grain Storage Volume

Storage

Storage type

Silo diameter (m)

Imperial: enter feet

Silo height (m)

Crop type

Grain moisture (%)

Receivable standard: wheat 12%, canola 8%

Silo volume = π × r² × height Tonnes = Volume (m³) × Grain density (t/m³) Grain densities (t/m³): Wheat 0.78 · Barley 0.62 · Canola 0.67 · Sorghum/Corn 0.72 · Oats 0.50
Allow 5–10% headspace for aeration. Check moisture before sealing storage — high moisture causes spoilage.

Reference: GRDC — Grain Storage Solutions · Stored Grain Australia

ℹ️ Results are estimates for planning purposes. Verify with current standards and a qualified professional.

1 What this calculator does

Calculates grain storage volume in cubic metres for round silos (cylinder + cone), flat-base bins and flat-floor shed storage. Converts volume to tonnes using crop-specific bulk density.

2 Formula & professional reasoning

Round silo:
V_cylinder = pi x r2 x Eave height
V_cone = (1/3) x pi x r2 x Cone height
V_total = V_cylinder + V_cone
Tonnes = V_total (m3) x Bulk density (t/m3)

Round silos have a cylindrical body and a conical hopper base. For a 45-degree hopper-bottom silo, cone height = radius. The cone adds about 10% of total volume and cannot be ignored. Bulk density varies by crop and moisture — wheat at 12% MC is ~780 kg/m3, canola at 7% MC is ~650 kg/m3. Using wheat bulk density for canola overstates tonne capacity by approximately 20%.

3 Worked examples

⚠️ Illustrative example only — not clinical or professional instruction.

Basic

Standard round silo — wheat capacity

Given: Diameter: 7 m (radius 3.5 m) | Eave height: 12 m | Cone height: 3.5 m | Wheat density: 780 kg/m3

Working:

V_cylinder: pi x 3.52 x 12 = 461.8 m3 | V_cone: (1/3) x pi x 3.52 x 3.5 = 44.9 m3 | V_total: 506.7 m3 | Tonnes: 506.7 x 0.780

Answer: 506.7 m3 | 395 tonnes wheat

💡 A 7 m x 12 m eave silo typically holds 380-420 t wheat depending on bulk density.

Standard

Same silo — canola capacity

Given: Same silo (506.7 m3) | Canola bulk density: 650 kg/m3

Working: Tonnes: 506.7 x 0.650

Answer: 329 tonnes canola

💡 Canola is 329 t vs 395 t wheat in the same silo — 17% less. Never apply wheat-based spec to canola planning.

Advanced

Flat-floor shed — wheat storage

Given: Shed: 30 m x 15 m | Fill height: 2.0 m | Wheat density: 780 kg/m3 | Apply 15% reduction for end-taper

Working: Volume: 30 x 15 x 2.0 x 0.85 = 765 m3 | Tonnes: 765 x 0.780

Answer: 765 m3 | 597 tonnes wheat

💡 Grain doesn't fill a flat shed square to the walls at the ends — apply 15% reduction for natural angle of repose.

4 Sanity check

Bulk densities at harvest moisture

Wheat 11-12% MC: 750-800 kg/m3 | Canola 7-8% MC: 620-680 kg/m3 | Barley 12% MC: 620-660 kg/m3 | Chickpeas: 750-780 kg/m3

Measure bulk density from the actual grain lot — moisture and variety affect it.

Manufacturer's tonne specs

Usually based on wheat at 775 kg/m3

For canola: multiply manufacturer's wheat tonne rating by 650/775 = 0.84.

Flat storage angle of repose

Wheat ~28 degrees | Canola ~25 degrees — apply 15% reduction to rectangular volume

Never exceed manufacturer's rated capacity

Structural failure under overloading

Silo structural failure is catastrophic and potentially fatal.

5 Common errors

Error	Cause	Consequence	Fix
Treating silo as pure cylinder — ignoring the cone	Simplifying the shape	Capacity understated 5-15%	Always add cone volume. For 45-degree hopper-bottom silo: cone height = radius.
Using wheat capacity for canola	Applying manufacturer's wheat-based spec	Canola capacity overstated by ~17%	Multiply wheat-based tonne capacity by 650/775 = 0.84 for canola.
No angle-of-repose reduction for flat-floor sheds	Using shed area x height directly	Capacity overstated 10-20%	Apply 15% reduction factor to theoretical rectangular volume for end-taper.
Used silo without structural certification	Secondhand silo of unknown origin	Risk of structural failure — catastrophic and fatal	Every silo needs current structural certification before filling.