Silage Pit Capacity Calculator & Tonnes & Days of Feed
Stores maize silage
“One accepted answer here saves a hundred people an hour each.
Size your silage store — from the pit dimensions and density get the volume in m³ and the tonnes of silage it holds, plus how many days it feeds your herd.
Enter your silage pit
Next: size the pit to your herd and season — fill quickly, roll and compact each layer well to push out air, then seal with sheeting and weight it down so the silage ferments cleanly instead of spoiling.
Well-compacted silage ≈ 600-750 kg/m³.
Silage pit — key facts
- Tonnes
- volume × density ÷ 1000
- Bunker volume
- L × W × H
- Clamp volume
- avg width × H × L
- Silage density
- ≈ 600–750 kg/m³
- Dairy cow intake
- ≈ 20–30 kg/day
- Days of feed
- tonnes ÷ daily intake
- Key to capacity
- good compaction & sealing
- Privacy
- Runs in your browser; nothing uploaded
Store enough feed for the lean season
Silage carries a herd through the dry or winter months when fresh fodder is scarce, but only if the pit holds enough. Capacity comes down to two things — the pit's volume and the silage's density — and density depends on how well you compact it. Get the maths right and you can size a pit to your herd and feeding period, or check whether an existing pit will see you through.
This tool turns your bunker or clamp dimensions and density into the volume in m³, the tonnes of silage, and the days of feed for your herd's daily intake. Compact heavily in thin layers and seal airtight to raise density and cut spoilage — that packs more feed into the same pit. Match the pit's face to your daily feed-out so silage stays fresh. Pair it with the Hay & Silage Storage, Livestock Feed and Cattle Stocking Rate tools.
Know the tonnage
Exact tonnes of silage a pit holds from its dimensions.
Match the herd
See how many days the pit feeds your animals.
Size a new pit
Test dimensions until the capacity meets your feeding period.
Value compaction
See how density (good rolling) raises effective capacity.
Frequently Asked Questions
How much silage does a pit hold?+
Multiply the pit's volume by the silage density. A rectangular bunker 10 × 4 × 2 m is 80 m³; at a well-compacted density of ~700 kg/m³ that's about 56 tonnes of silage. This tool computes the volume and tonnage for a bunker or a trench clamp from your dimensions and density.
What is the density of silage?+
Well-compacted silage is roughly 600–750 kg/m³ (fresh weight), depending on the crop, chop length, moisture and how hard it's rolled. Poorly compacted silage is lighter, holds less per pit and spoils more. Good compaction packs more tonnes into the same pit and excludes air.
How do I calculate a bunker silo capacity?+
For a rectangular bunker, volume = length × width × height (the filled height, in metres), then tonnes = volume × density ÷ 1,000. The tool does this and also handles a trench clamp with sloping sides (a trapezoidal cross-section). Enter your real internal, filled dimensions.
How long will my silage last?+
Divide the tonnage by the herd's daily silage intake: days = tonnes × 1,000 ÷ (animals × kg per animal per day). The tool computes the days of feed when you enter the herd size and feeding rate, so you can match the pit to the feeding period.
How much silage does a cow eat per day?+
A dairy cow typically eats about 20–30 kg of silage (fresh weight) a day as part of its ration, young or dry stock less. Use your actual feeding rate per animal. Enter it with your herd size and the tool tells you how many days the pit's silage will feed them.
What size silage pit do I need?+
Size it to the silage you must store: required tonnes ÷ density = volume needed, then choose dimensions to suit. Work back from your herd's daily intake × the number of feeding days. The tool lets you test pit dimensions until the tonnage and days of feed match your need.
Bunker or trench clamp — what's the difference?+
A bunker has vertical walls (rectangular cross-section); a trench or clamp often has sloping sides (trapezoidal cross-section), so its capacity uses the average of the top and bottom widths. The tool supports both — pick the shape and enter the relevant widths.
How do I reduce silage losses in the pit?+
Fill quickly, chop short, compact heavily in thin layers, seal airtight with sheeting weighted down, and feed out across a clean, fast-moving face to limit air exposure. Good density and sealing cut spoilage dramatically — and pack more feed into the pit, raising effective capacity.
Does the feed-out rate matter?+
Yes — once open, silage spoils if the face isn't used fast enough (aim to move across the whole face every few days). Size the pit's cross-section to your daily removal so you maintain a fresh face. A pit that's too wide for a small herd loses silage to spoilage at the face.
Can I use this for haylage or maize silage?+
Yes — the volume × density method applies to any ensiled fodder (maize, sorghum, grass, legume). Just use the appropriate density (maize silage is often denser than grass) and your feeding rate. The tool's default suits typical well-compacted silage; adjust the density for your crop.
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