Stock cover answers “how long will current stock last?” — units on hand divided by the average sales rate. Expressed in weeks or days, it’s the planner’s early-warning gauge for stockouts.
The example
320 on hand, 40/week.
| A | B | |
|---|---|---|
| 1 | Item | Value |
| 2 | On hand | 320 |
| 3 | Weekly sales | 40 → 8 weeks |
The formula
The formula:
How it works
How it works:
- Divide units on hand by the average sales rate (per week or per day).
- The result is weeks (or days) of cover — how long stock lasts at the current pace.
- Compare to your lead time: if cover < lead time, you’ll stock out before a reorder arrives.
- Use a trailing average of sales so a single spike doesn’t distort the figure.
Cover vs lead time is the alarm: if you have 3 weeks of cover but a 4-week supplier lead time, you’re already late to reorder. Planners often flag any SKU where cover - lead_time drops below a safety threshold — a single conditional-formatting rule turns the sheet into a watchlist.
Try it: interactive demo
On hand and weekly sales.
Variations
Days of cover
Daily rate:
Cover vs lead time
Risk flag:
Trailing average sales
Smooth the rate:
Pitfalls & errors
Match the unit. Weekly sales gives weeks of cover; daily sales gives days.
Average the rate. Use a trailing average so one big week doesn’t mislead.
Zero sales. A dead SKU gives #DIV/0! (infinite cover) — handle with IFERROR.
Practice workbook
Frequently asked questions
How do I calculate stock cover in Excel?
How do I know when to reorder from cover?
Why use an average sales rate?
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