You Did Not Forget the Toilet Paper; You Have No Reorder Point

You reached for the toilet paper and there was none. You blamed your memory. Your memory is not the issue. You were running the most critical supply in the house on the policy “notice when it’s gone,” which is not a policy — it is the absence of one. Warehouses solved this a century ago, and the solution fits on one line.

The buffer

Stop reordering when you run out. Reorder when you hit a reorder point: the stock level at which a new pack must be bought now so that fresh stock arrives before the last roll does.

reorder point =
    daily usage × restock lead time
  + safety stock        (the buffer for a bad week or a slow trip)

“Lead time” is just how long until you next realistically buy more — your weekly shop, or a delivery window. When stock falls to the reorder point, you buy. Not before (you’d hoard), not after (you’d run dry).

Worked example

A two-person household uses about one roll every two days, so usage is 0.5 rolls/day. You shop weekly, so worst case the next pack is 7 days away. You want a few days of cushion for guests or a missed trip — call safety stock 3 rolls.

(0.5 × 7) + 3 = 6.5  →  reorder at 7 rolls

When the cupboard drops to about seven rolls, the next pack goes on the list. That is the entire system. No app, no subscription, no panic aisle-run.

Why this beats “buy in bulk”

Bulk-buying hides the problem instead of solving it: a giant pack still hits zero, just less often and with no warning, because you are still reordering on empty. The reorder point works at any pack size — it just changes how often you cross it.

Apply it to everything that must never hit zero

• Toilet paper, dish soap, laundry detergent, coffee, pet food, prescriptions.
• For each, estimate daily usage, multiply by your restock lead time, add a small safety stock, and write the threshold on the shelf or a list.
• Re-derive once if your usage changes (a new flatmate, a new baby). Otherwise it is set-and-forget.

You don’t need a better memory. You need a number on the shelf.