Days of supply is the number everyone asks for and almost nobody computes the same way. At its simplest it is stock on hand divided by daily consumption. Both halves of that fraction hide decisions, and the decisions are where plans go wrong.
The stock is the easy half
On hand is a count, and counts are reported. The questions are when the count was taken, whether it includes stock in transit or only stock in the unit's possession, and whether the storage that holds it can actually be drawn from at the rate the plan assumes. A full tank that cannot be issued fast enough is a storage problem wearing a stock number.
The rate is where the argument lives
Daily consumption is not observed. It is derived: equipment on hand, multiplied by a planning factor for each item, adjusted for operational tempo, terrain, weather, and the phase of the operation. Two staffs with the same stock and the same equipment will report different days of supply if one assumes a higher tempo. Neither is wrong. They are planning for different fights, and the number should say which.
- Planning factors have sources. A fuel burn rate comes from a manual, a table, and a page, or from a named expert's judgment. Either is acceptable. Neither is acceptable unstated.
- Tempo is a choice. The same vehicle burns differently in a movement to contact than in a defense. The forecast should carry the tempo it assumed.
- The floor matters as much as the stock. Commanders set a level below which a unit is not permitted to fall. Days of supply to zero and days of supply to the floor are different numbers, and the second is the one that drives decisions.
How ALLCLASS computes it
The forecast derives consumption from each unit's equipment and the tempo in the order, projects stock forward against storage and the commander's floor, folds in scheduled resupply, and reports days of supply at any time step. Every value opens a card with the formula, the inputs, the planning factor and its citation, and the limits of the method. When a unit stops reporting, the last count is carried forward, the uncertainty widens by the day, and the cell shows a range instead of a false precision.
Why this matters to a buyer
The benchmark we propose for any pilot is simple: the staff's own plan and ALLCLASS, on the same inputs, scored on forecast accuracy against what the units later reported. Days of supply is the first number scored, because it is the first number briefed.