| Formula | Meaning | Example |
|---|---|---|
| (Usage × Frequency) + Buffer | Mark when to reorder based on consumption | 2 cups/week × 1 week + 1 cup = 3 cups remaining |
When to use: For containers where you can see the level (clear bottles, jars).
The action: Put rubber band or line at calculated level. When liquid hits that line, buy more.
Complete Example
Item: Olive oil Usage: 1/4 cup per week Shopping frequency: Every 2 weeks Buffer: 1/2 cup (safety margin)
Calculation:
- (0.25 cup/week × 2 weeks) + 0.5 cup buffer
- = 0.5 + 0.5
- = 1 cup from bottom
Action: Mark bottle at 1 cup line. When oil hits that line, add to shopping list.
Why Buffer Matters
Without buffer: You calculate perfectly, but get busy and skip a shopping trip. Now you’re out.
With buffer: You have safety margin. Miss one trip? Still have oil.
Typical buffers:
- High-use items (daily): 3-5 day buffer
- Medium-use (weekly): 1 week buffer
- Low-use (monthly): 2 week buffer
North: Where this comes from
- Inventory Management Theory
- Reorder Point (manufacturing concept)
South: Where this leads
- Visual Zoning (making levels obvious)
West: What’s similar?
- Safety Stock (manufacturing buffer inventory)
- Minimum Balance (banking overdraft prevention)