Order weekly or monthly? What your reorder cycle really costs

Every order pays two bills

Every purchase order charges you twice, and the two charges move in opposite directions.

The first bill is charged per order, more or less regardless of order size. The freight or LTL minimum you pay whether the pallet is full or half empty. The time to build the PO, send it, chase a confirmation, and follow up when the confirmation doesn't come. The receiving and put-away work at the other end. Raise twice as many orders and you pay this bill twice as many times.

The second bill is charged per unit of cover the order must carry until the next one lands. Cash sitting in stock instead of in your account. Markdown risk that accumulates the longer a unit ages on a slow-turning shelf. Order twice as much at a time and you pay this bill on roughly twice the average inventory.

Ordering frequency moves money between the two bills. It never removes it. Which is why the useful question isn't "how often should I order?" — it's "at what gap between orders do the two bills together add up to the least?"

The gap between orders is inventory you have to own

Lengthening the gap between orders doesn't just move delivery dates on a calendar. It raises the quantity on every line of every order, and it raises the buffer sitting behind that quantity.

Start with the stock itself. Under steady demand, an order arrives, gets drawn down to nothing, and is replaced — so the average amount on hand across the cycle is about half the order quantity. Double the gap and you double the order quantity, which doubles the average cycle stock. That's the inventory you'd carry even if demand were perfectly predictable, before any buffer at all.

average cycle stock ≈ order quantity ÷ 2

The buffer moves with it. Because each order has to survive the whole protection interval — the lead time plus the gap until the next one lands — a longer cycle stretches the cover and the buffer protecting it, since more days means more accumulated forecast error before you get another chance to correct.

Put both bills on the same axis and the shape is clear: per-order costs fall as you order less often, and carried stock rises. So there's a balance point, not a direction — the classic economic-order-quantity result is that at the optimum, the fixed cost of ordering and the cost of holding are equal.

Where the wrong cycle shows up in your numbers

A badly-sized cycle doesn't announce itself. It shows up as two symptoms at opposite ends of the same problem, both surfaced in the Smart Buying Table as findings ranked by money at stake: items that run out before a reorder can land, and capital tied up in overstock.

The trick is to read a run of those findings as a cycle diagnosis, not a pile of per-SKU accidents. One SKU short is a forecast miss. The same supplier's SKUs short every third week, in the same window, is a cadence problem — the gap you've asked each order to bridge is longer than the stock it was allowed to carry.

The overstock end reads the same way in reverse. A very high days-of-stock number on a slow mover is often the cycle asking that SKU to bridge a gap it doesn't sell fast enough to justify; the quantity wasn't wrong given the cycle, the cycle was wrong for that item's velocity. Because the buying table shows the cover period as its own line in the suggestion math, before subtracting incoming stock from open POs and what's on hand, you can see how many days of cover a suggestion is buying — where a cadence problem shows up before it becomes a markdown.

Price the trade per supplier, not per store

That the cadence belongs to the supplier rather than to your calendar is settled ground; what's left is where each supplier's should land.

The answer is set by the size of that supplier's per-order bill. The more a single order costs to place and receive, the further out the balance point sits before the fixed-cost savings stop paying for the extra stock. A supplier whose orders cost almost nothing to raise has a balance point close in: no reason to pay to carry a month of cover. A supplier whose per-order bill is a container booking and weeks of coordination has one much further out, and the stock between arrivals is what that buys. Same trade, different bill.

Which is why Reorder Cycle in Assisty is a stored field on the supplier, alongside Lead Time, Min Stock Cover Days, and order minimums and maximums. Set them once and the buying table's suggested quantities use them automatically — computed from sales velocity, lead times, and incoming stock, then rounded to case sizes and capped at maximum stock levels. Where one product doesn't follow its supplier's defaults, override it per variant: supplier SKU, cost, minimum order quantity, case quantity. And the params can be changed conversationally, with the change flowing into the next run of suggestions.

Assisty won't tell you what your cycle should be — it doesn't know what your freight costs or what your capital is worth. It holds the cycle you decide on and applies it consistently to every quantity it suggests.

So here's the test. Pick one supplier. Name the per-order cost you actually pay them. Then look at what the current cycle is asking each of their SKUs to carry between deliveries. If the cover is worth more than the order costs, order more often.