Hay Moisture, Dry Matter & Price Comparison Calculator
Compare hay lots fairly: tons of dry matter and water in a load, price per ton of dry matter and per pound of crude protein or TDN, whether the baling moisture is safe for small squares, rounds or large squares, heating and mould risk, the weight loss to expect as bales cure, and which of two lots is the better buy.
How it works
dry matter = 1 − moisture · $/ton DM = $/ton delivered ÷ DM fraction · lb protein per ton = 2000 × DM × CP% · $/lb CP = $/ton ÷ lb CP per ton · curing shrink % ≈ (moisture − 12%) ÷ (1 − 12%) · safe baling moisture: small squares ≤ 20%, rounds ≤ 18%, large squares ≤ 16%; baleage 40–60%
Hay is bought by the ton but fed by the pound of dry matter, and a load that is a few points wetter delivers proportionally less feed and more water, which is why the honest comparison between lots divides the price by the dry-matter fraction and then by the protein or energy each pound of dry matter carries. Moisture also decides whether hay will keep: above the safe limit for its bale density it heats as microbes respire, losing feed value, moulding and, in the worst range, catching fire, unless it is preserved with acid or wrapped and fermented as baleage. The curing loss and the respiration loss both come out of the buyer's ton if it is weighed wet.
Worked example
Twenty tons of alfalfa-grass at 16% moisture and $180 a ton contain 16.8 tons of dry matter and 3.2 tons of water — $214 per ton of dry matter and about 60¢ per pound of protein at 18% CP. Drier hay at 11% and $200 a ton is $225 per DM ton, so lot A is cheaper on dry matter, but lot B's 20% protein makes its protein cheaper at 56¢ a pound. Sixteen percent is borderline for round bales and will lose about 4.5% of its weight curing down to 12%.
Frequently asked questions
What moisture should hay be baled at?
Small squares up to about 18–20%, round bales 16–18%, large squares 14–16% because dense bales trap heat. Above that use a propionic-acid preservative (to ~25%) or wrap it as baleage at 40–60%; 25–35% unpreserved dry hay is the spontaneous-combustion danger zone.
Is relative feed value (RFV) better than CP and TDN?
RFV or RFQ combine fibre digestibility and intake into one index and are what most hay markets quote; use them to rank lots, then price per ton of dry matter (or per point of RFV per DM ton) to compare cost.
Related calculators
Agronomic rules of thumb and standard grain-trade formulas from extension services. Local elevators, labs and equipment dealers publish their own schedules and specifications — use those where they differ, and confirm lime and fertilizer rates with a current soil test.