Inventory Stock Calculator
Work out your reorder point and how much stock to order right now.
Recent
Formula
How the calculation works
The reorder point is daily sales times the lead time plus a safety margin, the level at which you must order again.
Stock to order is that point minus what you hold, and it is never negative.
Days of stock shows how long the current stock lasts, which is a quick warning if it is low.
Common mistakes
- Setting the safety margin to zero, which leaves no buffer when sales spike or a delivery is late.
- Using average sales over a whole year when demand is seasonal, which mis-sets the reorder point.
When to use it
- Use it to decide when to reorder and how many units to bring in.
- It is not a forecast; it assumes the daily sales figure you enter holds.
Worked example
Selling 20 a day with 7 days of lead time and 3 days of safety stock needs a reorder point of 200, so with 100 in stock you should order 100 more.
Common questions
What is a reorder point?
It is the stock level at which you place a new order so it arrives before you run out.
Why add safety stock?
It covers delays and demand spikes so a late delivery does not stop sales.
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