Milling Math

How to Calculate Mill Throughput, Moisture Loss, and Energy Per Ton in Grain and Feed Handling

A step-by-step walkthrough of the five formulas that run a grain mill or feed plant, with real units, worked numbers, and where every input comes from.

Mill throughput is the anchor calculation. Take clean grain into the first break in kg per hour, then throughput equals mass processed divided by run hours. A roller mill fed 18,000 kg over a 3.0 hour run posts 6,000 kg/h, or 6.0 t/h. Convert to bushels using the crop density: wheat at 27.2 kg per bushel gives 6,000 divided by 27.2, about 220 bu/h. Pull the mass figure from the intake scale ticket, not the truck weight, because tare and foreign material inflate gross by 1.5 to 3 percent. The Mill Throughput calculator handles the unit switches so you compare wheat, corn, and soy on the same axis.

Moisture loss drives shrink, and shrink is real tonnage you paid for but cannot sell. Percent moisture removed equals (initial moisture minus final moisture) divided by (100 minus final moisture), times 100. Corn dried from 18.0 percent to 15.0 percent loses (18 minus 15) over (100 minus 15), which is 3 over 85, or 3.53 percent of mass. On a 40 t lot that is 1.41 t gone as water vapor. Weigh moisture with a calibrated NIR or oven method on a composite sample, not a single probe. The Moisture Loss calculator returns both the percent and the physical kilograms so your inventory reconciles.

Bin capacity keeps you from over or under filling storage and misreporting inventory. For a cylindrical bin, volume equals pi times radius squared times fill height. A 5.5 m diameter bin filled to 9.0 m holds 3.14159 times 2.75 squared times 9.0, about 213.8 cubic meters. Multiply by bulk density: wheat at 772 kg per cubic meter yields roughly 165 t. Add the cone if the bin has a hopper bottom, and derate usable height by 0.3 to 0.5 m for the peak angle of repose. Bin Capacity does the geometry plus density lookup so you avoid the classic full versus workable mix-up.

Batch blend accuracy tells you whether a formulated ration actually matches the recipe. For each ingredient, deviation equals (actual weight minus target weight) divided by target weight, times 100. A ration calling for 250 kg of soybean meal that scales in at 246 kg runs a deviation of minus 1.6 percent. Aggregate across ingredients using absolute deviations weighted by inclusion rate to get a batch score. Micro-ingredients under 5 kg swing hardest, so a 0.4 kg overshoot on a 4 kg premix is a 10 percent error. Batch Blend Accuracy flags which line item broke tolerance before the batch discharges.

Energy per ton converts your power bill into a per-unit cost driver and a maintenance signal. It equals total kilowatt hours consumed divided by tons produced. A hammermill drawing an average 110 kW over a 6.0 hour run uses 660 kWh; against 48 t milled, that is 13.75 kWh/t. Pull kWh from a submeter on the mill motor, not the whole-plant meter, or you fold in conveyors, aspiration, and lighting. Fine grinds and dull hammers push this number up 15 to 30 percent, so a rising trend is an early wear alarm. Energy Per Ton isolates the specific energy so you can track it shift over shift.

Yield loss ties the day together by comparing finished good out against clean grain in. Yield equals finished product mass divided by input mass, times 100; loss is the complement. If 42 t of clean wheat produces 31.5 t of flour, extraction is 75.0 percent, and total loss including bran, germ, and dust runs 25 percent, of which 1 to 2 points is invisible handling loss. Reconcile against the moisture shrink you already computed so you do not double count water as physical loss. The Yield Loss calculator separates targeted byproduct from unaccounted loss, which is where money quietly leaks.

Dust collection load matters because undersized aspiration chokes throughput and creates an explosion hazard. Required airflow equals the sum of pickup volumes across hoods, sized by capture velocity times duct area. A transfer point needing 3.5 m/s across a 0.30 by 0.20 m hood draws 3.5 times 0.06, about 0.21 cubic meters per second, or roughly 445 CFM. Sum every pickup, add 10 to 15 percent for duct leakage, and match against your baghouse rating. Dust Collection Load totals the pickups so you know whether a new line will starve the existing collector.

Chain these calculations rather than running them in isolation. Throughput sets the tons denominator for both energy per ton and cost per ton; moisture loss adjusts the mass that flows into yield; bin capacity caps what throughput can stage. Run them in that order at shift close, using scale tickets, submeter reads, and a composite moisture sample, and your numbers reconcile to within 0.5 percent. Save each run so a drifting energy per ton or a widening blend deviation shows up as a trend line, not a surprise on the month-end reconciliation.

Published 2026-07-01.