How is the volume worked out for each shape?

A bunker is length times width times average settled height. A wedge clamp uses the average of its tall and short ends as the mean height. A round pile is treated as a cone, one-third times the base area times height. All are in cubic metres before applying density.

What bulk density should I use?

Well-consolidated grass and maize silage in a bunker typically runs 650 to 800 kg per cubic metre as fed, higher with good packing and lower for loose or dry crops. A poorly packed pile can be 500 kg or less. Use a measured figure where possible because density drives the result.

Why does moisture matter for an inventory?

Animals are fed on a dry-matter basis, so wet silage weighs more but feeds less per tonne. Converting fresh tonnes to dry-matter tonnes, by multiplying by one minus the moisture fraction, tells you how much actual feed value is in the clamp.

Is the calculated tonnage the amount I can feed?

Not entirely. There are always losses from surface spoilage, shoulders, and feed-out face management, commonly 5 to 15 percent. Treat the figure as gross inventory and discount for expected waste when planning how many days it will last.

Can I use imperial units?

Enter dimensions in metres and density in kg per cubic metre for this tool. To convert, one foot is 0.3048 m and 1 lb per cubic foot is about 16.02 kg per cubic metre. The output tonnes are metric (1000 kg).

Silage Tonnage Calculator

Knowing how much silage is actually in the clamp is the difference between running short in February and wasting forage. This calculator estimates the fresh and dry-matter tonnes in a bunker, wedge, or pile from its dimensions and a bulk density, so you can inventory feed and plan the winter accurately.

How it works

The volume formula depends on the shape, and density and moisture convert that volume into feed tonnes:

bunker volume = length × width × height
wedge volume  = length × width × (tall + short height) / 2
pile (cone)   = (1/3) × π × radius² × height
fresh tonnes  = volume (m³) × density (kg/m³) / 1000
DM tonnes     = fresh tonnes × (1 − moisture% / 100)

Because settled silage is denser than fresh-cut crop, use the as-fed bulk density of consolidated silage rather than the chopped crop, and measure it if you can — it is the single biggest driver of the answer.

Example and tips

A bunker 30 m long, 8 m wide and 2.2 m of settled silage holds 528 m³. At 720 kg/m³ that is about 380 fresh tonnes, and at 30 percent dry matter roughly 114 tonnes of dry matter. Subtract a realistic spoilage allowance of around 10 percent when planning feed-out days, and re-measure the face height as the clamp empties to keep your remaining-inventory estimate honest.