How to use this calculator
- Enter or choose units.
- Enter or choose length.
- Enter or choose width.
- Enter or choose average height of fodder.
- Enter or choose share of the space filled.
- The days of feed updates as you type. Use Copy result or Share to keep it.
Method
Volume = L × W × H × Fill%; Stored = Volume × Density; Days = Stored × (1 − Losses%) ÷ (Animals × Intake)
- Density
- mass of fodder per unit volume as stored (1 lb/ft³ = 16.018 kg/m³)
- Losses
- dry-matter loss, spoilage at the face and feed-out waste
- Intake
- as-fed fodder per animal per day
Worked example
- Volume = 30 × 10 × 3 = 900 m³.
- Stored = 900 × 650 kg/m³ = 585 t; after 10% losses = 526.5 t.
- Days = 526,500 kg ÷ (50 × 35 kg) = 526,500 ÷ 1,750 = 300.9 days.
A 30 × 10 m clamp filled 3 m deep holds about 585 t of silage, enough for 50 cows eating 35 kg a day for about 301 days.
What the result means
Compare the days of feed with the length of your feeding period; if it falls short, plan bought-in fodder early. Measuring the actual density with a core sample improves the estimate more than anything else.
Assumptions and limits
- The store is a rectangular block of fodder with an even height.
- Sloped clamp walls and domed tops are not modelled; use an average height.
- Intake is as-fed, so a change in dry matter changes the days of feed.
Questions
What bulk density should I use?
It varies widely: well-compacted wet silage is much denser than dry hay, and bales differ by size and press. Weigh a few bales or take a core sample from the clamp.
Should I count feed in kg as fed or dry matter?
Either, as long as the density and intake use the same basis. This page uses as-fed weight for both.