The question "do we need to reorder this yet?" comes up in every dental practice. If you answer it on gut feeling each time, you order too early, too late or too much. A minimum stock level per product takes away that doubt. In this article you will read how to calculate it, and how to keep your stock as small as possible without ever running out.
What is a minimum stock level?
The minimum stock level is the quantity below which you reorder. It is chosen so you still have enough to work with until the new delivery arrives, with a small reserve for unexpected use.
You can also set a maximum stock level: the quantity you want on hand after a delivery. The maximum stops you from overstocking, with expired products and full cabinets as a result.
The formula
Minimum stock = usage per week × (lead time in weeks + buffer in weeks)
- Usage per week is how much you use on average.
- Lead time is the time between your order and the moment the product is in your cabinet. Also count the time until your next fixed ordering moment.
- Buffer is your reserve for busy weeks or a delivery that arrives late.
Three examples
| Product | Usage per week | Lead time + buffer | Minimum |
|---|---|---|---|
| Nitrile gloves M | 2 boxes | 1 + 1 week | 4 boxes |
| Composite A2 | 3 syringes | 1 + 1 week | 6 syringes |
| Anesthetic cartridges | 1 box | 1 + 0.5 week | 2 boxes |
For the cartridges you end up with one and a half boxes. Always round up: you can't order half a box, and you can't work without anesthetic.
Measuring your usage
The formula is only as good as your numbers. If you don't know how much you use, count your stock at the start of every week for four weeks. The difference between two counts, plus what was delivered that week, is your weekly usage.
If you have had a system for a while that tracks what leaves the shelf, you can read the usage from there.
How big should your buffer be?
Not every product deserves the same reserve:
- Essential products, like anesthetics and gloves, get a larger buffer. A shortage means you have to move appointments.
- Expensive products, like implants and composites, you keep as tight as is responsible. Every extra syringe in the cabinet is money sitting still.
- Products with a short shelf life you also keep tight, so you use them up before they expire.
Setting the maximum stock level
A simple rule of thumb: maximum = minimum + what you use between two ordering moments. If you order gloves every two weeks, the maximum is 4 + 2 × 2 = 8 boxes.
For cheap products you buy in large quantities, like cups and bibs, the maximum can be higher. For expensive or perishable products you keep it close to the minimum.
Taking seasons into account
Usage is not the same all year. In many practices it is lower in summer, and often higher toward the end of the year. So recalculate your minimum and maximum every quarter, and lower them for quiet periods so you don't go into the holidays with a full cabinet.
How often should you recount?
Even with a good system, errors creep into your count. Recount your A products every month, your B products every quarter and the rest twice a year. A count sheet you can print makes that work a lot faster.
Minimum and maximum in Swyp
In Swyp you set a minimum and a maximum per product. When the stock drops below the minimum, the product appears on your low-stock list. From that list you create one reorder, split across your suppliers for the lowest total. For a full count you print count sheets straight from Swyp.
Also read our guide to inventory management in the dental practice and what to look for in dental inventory software.
