Silage Storage Calculator

A well-packed corn silage bunker typically runs 40-45 lb/cu ft as-fed; 44 lb/cu ft is a reasonable default. Haylage and grass silage typically pack a bit lighter, roughly 35-40 lb/cu ft; 38 lb/cu ft is a reasonable default. Both figures assume good packing practice - thin layers, adequate packing weight, and enough time on the pile. Weigh a known volume of your own silage if you want a site-specific number.

They answer two different questions. The animal's intake percent (commonly 2-3.5% of body weight) tells you how many pounds of dry matter the animal needs to eat. The silage's dry-matter percent (commonly 30-40% for corn silage, higher for wilted haylage) tells you how many as-fed, wet pounds of silage contain that much dry matter. Skipping the second conversion badly overstates feeding-days, because a lot of silage's as-fed weight is water the animal doesn't get nutrition from.

A well-managed, well-sealed bunker or pile commonly loses about 7-15% of its dry matter to spoilage at the exposed face, the top crust, and any effluent runoff. Poorly packed, poorly sealed, or long, slow-feeding piles can lose 20% or more. The default of 10% here is a reasonable middle estimate for a reasonably well-managed operation; tighten it toward 7-8% for excellent management (tight plastic, gravel bags, fast feed-out) or widen it toward 15-20% if the pile sits uncovered or is fed out slowly.

Use an average packed height, not the tallest point. Bunker piles and drive-over piles are almost never a flat-topped rectangular block - they typically crown in the middle and taper at the edges - so measuring only the peak overstates the volume. Taking a few height readings across the pile and averaging them (or estimating a trapezoidal cross-section by hand) gives a more realistic volume than a single peak measurement.

The tonnage math (volume × density) still applies, but a rectangular-prism volume formula does not match a cylindrical tower silo's shape, and packed density in a tower increases with depth from the weight of the material above rather than staying uniform. This calculator is built for rectangular bunkers and drive-over piles; for a cylindrical tower silo, use a cylinder-volume calculation with an average density figure appropriate to the fill depth.