Inventory Projection: From a Stock Balance to Feasible Order Releases
Maintained by IronTandem. Methods, checks and corrections.
Reconcile a six-period inventory plan, explain its three suggested receipts, and test how minimum orders and lead time change the decision.
Start with a dated question
A stock snapshot tells you what is available now. Inventory position can include inbound orders without showing whether they arrive in time. A dated projection instead asks what balance remains after each receipt and demand event. In this fictional example, planning starts October 17, 2026 with 180 units, a 40-unit safety target, a fourteen-calendar-day lead time, no minimum order and an order multiple of 20. The six CSV rows are weekly demand buckets on their entered dates. They are not a record of a real customer or a forecast supplied by IronTandem.
Keep confirmed receipts separate from suggestions
Scheduled receipts are 60 units in W2 and 120 in W4. Demand across the six rows totals 560 units. With no new supply, the final balance is 180 opening + 180 scheduled - 560 demand = -200. A negative baseline is unmet demand carried forward by this model, not physical negative stock on a shelf. Suggested orders must stay in a separate column; adding them to the scheduled-receipt file before an order is actually confirmed would make an unapproved plan look like committed supply.
Worked example: the first requirement
W1 consumes 80 from 180, leaving 100. W2 adds the scheduled 60 and consumes 100, leaving 60. W3 consumes another 90, so its balance before new supply is -30. Reaching the safety target of 40 requires 70 units. The order multiple is 20, therefore the suggestion rounds up to 80, not 70. Planned ending stock becomes 50. This ten-unit excess is a consequence of the chosen lot size, not an extra safety-stock target. The downloadable CSV contains demand and confirmed receipts only, so the calculation can reproduce the suggestion.
Reconcile the rest of the horizon
W4 starts from planned stock of 50, receives 120 and consumes 110, ending at 60 without a suggestion. W5 consumes 80; its -20 pre-supply balance needs 60 to reach 40, already a complete multiple of 20. W6 then needs another 100 to reach 40 after consuming 100. Suggestions total 80 + 60 + 100 = 240. The independent horizon check is -200 baseline + 240 suggested = 40 ending planned stock. Reconcile both individual rows and the horizon: a correct grand total alone could conceal supply assigned to the wrong date.
Test a minimum-order constraint
Change only the minimum order to 100. W3 now receives 100 rather than 80 and ends at 70. W4 ends at 80. W5 consumes all 80 and requires supply to restore the target; the minimum again forces 100. W6 consumes that 100 and triggers another minimum order of 100. Total suggestions rise to 300 and final planned stock to 100. The policy has not improved the demand forecast. It has increased purchase quantity and ending exposure to respect the entered minimum, a tradeoff that should be checked against storage, expiry and supplier terms.
Date the releases before calling the plan feasible
In the base case, the W3 receipt date is November 2. Fourteen calendar days earlier is October 19, after the October 17 planning snapshot, so its release is not late under the model. Increase only lead time to 28 days and that release moves to October 5, before the snapshot. One suggestion is then flagged late. The calculator still shows the quantity needed, but it cannot create the missed lead time. Review an expedite, alternative supply, changed demand date or an acknowledged service shortfall rather than calling the original receipt achievable.
Choose the appropriate next check
This projection follows one consistent stock pool and treats the entered receipt and demand dates as its event boundary. It does not explode a bill of materials, reserve supplier capacity, select working-day calendars or prove availability inside a weekly bucket. Use reorder point to examine a continuous-review trigger, min/max for that specific replenishment policy, and days of supply for a constant-demand snapshot. Those tools may legitimately answer differently because they answer different questions. Preserve the source file and assumptions with a decision; replace a suggestion with confirmed supply only after the responsible purchasing process has approved it.
The base-case stock trace
| Period | Demand | Scheduled receipt | Suggested receipt | Planned ending stock |
|---|---|---|---|---|
| W1 | 80 | 0 | 0 | 100 |
| W2 | 100 | 60 | 0 | 60 |
| W3 | 90 | 0 | 80 | 50 |
| W4 | 110 | 120 | 0 | 60 |
| W5 | 80 | 0 | 60 | 40 |
| W6 | 100 | 0 | 100 | 40 |
Reproduce the example
The sample file contains fictional figures only. Keep the dates and assumptions in the walkthrough when comparing its result.