Turn silage-bag diameter × usable length and packing density into wet tons — with optional dry-matter tons from DM %.
Use this for bag inventory or to size how many bags you need for a harvest tonnage target.
Usable length is often bag length minus about two diameters for sealed ends (UW Extension style). Density varies with crop and packing — adjust from local experience.
Usable length = bag length − 2 × (end_allowance × diameter). Volume = πr² × usable length. Tons from density.
usable_L = length − 2 × end_factor × diameter
ft³ = π × (D/2)² × usable_L
wet_tons = ft³ × density_lb_ft3 ÷ 2,000
dm_tons = wet_tons × (DM% ÷ 100)
Default end factor 1 means one diameter of seal at each end (two diameters total).
8 ft diameter, 200 ft bag, end factor 1 → usable 184 ft → volume ≈ 9,248 ft³. At 40 lb/ft³ → ≈ 185 wet tons; at 35% DM → ≈ 65 DM tons.
Assumptions: cylindrical fill; uniform density; end allowances approximate seals.
Limits: underfilled bags and soft packs hold less; spoilage not deducted.
Responsibility: verify with scales for sales, insurance, and CFAP-style reporting.
If you know lb DM/ft³, wet density ≈ DM_density ÷ (DM%/100). Example: 14 lb DM/ft³ at 35% DM ≈ 40 lb as-fed/ft³.
Same geometry — change density and DM% for the crop.
If seals use less than one diameter each end, lower the end allowance factor.