Silage Tonnage Calculator
Estimate tons of silage in a bunker, pile, upright silo or bag, plus feeding days and safe daily face removal.
Your numbers
48,000 ft³ at 14.0 lb DM/ft³, 67% moisture
1,020 tons as fed
- Dry matter tons
- 336 tons DM
- Usable tons after shrink
- 896 tons
- Days of feed for this head count
- 269 days
- You are only removing about 3.9 in/day of face, below the 6 in/day minimum — expect heating and spoilage at the face. Narrow the bunker or add more head to speed removal.
- Settled depth, not loose-fill height, drives this number — a freshly filled pile can settle 20-30% before it stabilizes.
- Budgeted shrink of 12% already reduces the usable tons; poorly sealed or loosely packed silage can run shrink well above that.
Show the math
- Volume100 ft × 40 ft × 12 ft = 48,000 ft³
- Dry matter stored48,000 ft³ × 14.0 lb DM/ft³ = 672,000 lb DM
- As-fed weight672,000 lb DM ÷ 33% DM = 2,036,364 lb as fed
- As-fed tons2,036,364 lb ÷ 2,000 = 1,018.2 tons
- Usable tons after shrink1,018.2 × (100% − 12%) = 896.0 tons
- Daily as-fed pulled100 head × 66.7 lb as fed/head = 6,667 lb/day
- Days of feed1,792,000 lb ÷ 6,667 lb/day = 269 days
- Daily face removal≈ 3.9 in/day off the feedout face
Assumptions this calculator used
Nothing here is hidden. Change any figure you have better local data for.
Fermentation, spoilage and seepage losses in a covered, well-packed structure. Source: Iowa State University Extension, silage storage losses.
%Below this, expect heating and secondary fermentation at the face. Source: Penn State Extension, silage bunker management.
in/day
How to calculate silage tonnage
Silage tonnage comes down to three numbers most operations already have: the settled volume of the structure, how densely it was packed, and the moisture of the crop. Get any one of the three wrong and the tonnage estimate can be off by 20% or more, which is why packing density and settled depth — not loose-fill height — matter more than the tape measure alone.
Bunker/pile ft³ = length × width × settled depth
Silo/bag ft³ = π × radius² × height (or length)
lb DM stored = ft³ × lb DM/ft³ packing density
Tons as fed = (lb DM ÷ dry matter %) ÷ 2,000
Worked example
A bunker 100 ft long, 40 ft wide, packed to a settled depth of 12 ft, at 14 lb DM/ft³ and 67% moisture holds 48,000 ft³ × 14 lb DM/ft³ = 672,000 lb DM, or 672,000 ÷ 33% DM ≈ 2,036,364 lb as fed — just over 1,018 tons as fed. After 12% shrink that is about 896 usable tons, enough to feed 100 head at 22 lb DM intake (66.7 lb as-fed/head/day) for roughly 269 days.
Common mistakes
- Using loose-fill height instead of settled depth. A freshly filled pile settles 20-30%; measuring the day you finish filling overstates tonnage badly.
- Guessing at packing density. A thin-layer, well-rolled bunker can run 15-16 lb DM/ft³ while a rushed fill with thick layers can fall to 10-11 — nearly a third less feed in the same footprint.
- Ignoring shrink entirely. The geometric tonnage this calculator gives you is what went in the pile, not what comes out. Budget 8-15% shrink for a well-managed, covered structure.
- Feeding out too slow a face. Not removing enough face per day lets air penetrate and heats the pile, which is a management problem this calculator can flag but a wider bunker or more head can fix.
Silage density and yield by moisture and packing
Typical dry matter and as-fed density figures for corn silage and haylage at common packing levels.
| Silage | Moisture | Packing quality | lb DM/ft³ | lb as-fed/ft³ |
|---|---|---|---|---|
| Corn silage | 65% | Well packed | 15-16 | 43-46 |
| Corn silage | 67% | Well packed | 14-15 | 42-45 |
| Corn silage | 67% | Average packing | 12-13 | 36-39 |
| Corn silage | 70% | Poorly packed | 10-11 | 33-37 |
| Corn silage | 60% (dry) | Well packed | 13-14 | 33-35 |
| Haylage (legume) | 55% | Well packed | 13-14 | 29-31 |
| Haylage (legume) | 60% | Well packed | 12-13 | 30-33 |
| Haylage (grass) | 60% | Average packing | 11-12 | 28-30 |
| Upright silo (avg column) | 65% | Self-packed by weight | 13-15 | 37-43 |
| Bag silage | 65% | Machine packed | 13-15 | 37-43 |
Calculators to run next
- Bunk Space CalculatorUse when timid cattle are falling behind or you are laying out a new pen.
- Dry Matter Intake CalculatorStart here — intake sets the size of every ration and feed budget that follows.
- Cattle Protein Supplement CalculatorUse when the hay tests short on protein and you need a feeding rate and a cost.
- Cost Per Pound of Gain CalculatorUse when deciding whether to feed cattle longer or sell them now.
- Feed Conversion Ratio CalculatorUse to judge how efficiently a pen is turning feed into pounds.
- Creep Feed CalculatorUse before rolling a creep feeder out to the calves this summer.
Questions ranchers ask
How do I calculate tons of silage in a bunker or pile?
Multiply length by width by average settled depth to get cubic feet, then multiply by the packing density in pounds of dry matter per cubic foot and divide by the dry matter percentage to get as-fed pounds. Divide by 2,000 for tons. Settled depth, not the height you drove over, is what matters — piles settle 20 to 30% from loose fill.
What packing density should I use for corn silage?
Well-packed corn silage in a bunker typically runs 14 to 16 lb of dry matter per cubic foot with an adequate packing tractor and thin layers. Poorly packed silage can fall to 10 to 12 lb DM/ft3, which both loses more tonnage to spoilage and stores less feed in the same footprint.
How much silage does a bag hold?
A 10 ft diameter, 200 ft bag at typical packing density holds roughly 180 to 220 tons as fed, depending on moisture and how well the bagger packed it. Use the bag's rated capacity from the manufacturer as a check against this calculator.
How many days will a silage pile last?
Divide total as-fed tons by daily as-fed pounds fed (head count times lb intake per head per day), then convert to days. A 500-ton pile feeding 100 cows at 25 lb as-fed per day (2,500 lb/day) lasts about 400 days.
How much face should I remove from a silage bunker each day?
To prevent secondary fermentation and heating, remove at least 4 to 6 inches of face per day in cool weather and 6 to 12 inches per day in warm weather. If your daily intake does not remove that much face, narrow the feedout face or switch to a smaller structure.
Why does my actual tonnage come in lower than the calculation?
Shrink. Top and side spoilage, seepage, and fermentation losses typically remove 8 to 15% of the dry matter that went into a bunker or pile, more in an uncovered or poorly packed one. Budget for shrink separately from the geometric tonnage this calculator gives you.
Is upright silo tonnage calculated differently than a bunker?
The geometry changes — volume is based on the cylinder (radius squared times pi times height) rather than length times width times depth — but the same dry matter and density logic applies. Upright silos typically pack denser toward the bottom due to the weight of silage above, so density can be treated as an average across the structure.
How much moisture should corn silage be harvested at?
Bunkers and piles pack best at 65 to 70% moisture (30 to 35% dry matter); wetter silage packs denser but risks seepage and effluent loss, and drier silage above 70% dry matter is difficult to pack and prone to mold pockets.
Know your feed inventory before you buy or sell cattle
Running out of silage mid-winter forces rushed, expensive decisions — buying cattle, buying feed, or selling stock at the wrong time of year. When the numbers say you need to adjust head count, source or move cattle on Agrilot, where every lot carries verified weights and seller records instead of a guess.