Reorder point formula (and safety stock)
How little is too little? That’s exactly what your Reorder Point will help you determine. Let’s talk about the concept of reorder points, safety stock, and how to put those numbers together to make sure you have the right amount of stock on-hand.
When you start your business off you’re probably making orders based on your gut instinct and the money you have on hand, but your reordering can be even more efficient with a reorder point formula. This post will show you what that is, and what numbers you’ll use to come up with a reorder point.
How to calculate reorder point
The thing to know about a reorder point is that it’s not a static number. It’s based on your own purchase and sales cycles, and it varies on a per-product basis. However, once you have a handle on patterns in your purchase and sales orders for a particular product, you’re ready to start putting the variables together.
The reorder point formula is:
Calculating average daily unit sales
Take the case of Archon Optical and their Ghost glasses. Here are the sales of the Ghost over the last three months:
If we total those numbers, we get 190 total units sold over the past 90 days. That means that the daily sales for the Ghost is 2.11 per day.
Calculating average delivery lead time
Average delivery lead time is simply the amount of time it usually takes for your shipments of a particular product to arrive. You’ll want to have a couple of purchase orders on-hand to check the numbers for this, as the delivery times can vary based on the quantity you order, as well as when you order it. There are a few different ways to calculate this, but averaging things out over the past few months can help provide some context.
In the case of Archon Optical, here are a few purchase orders for the last three month of Ghost shipments:
If you add the total delivery time (15 days ) and divide it by the number of orders (3 orders), then that’s an average lead time of five days for the product to arrive.
How to calculate safety stock quickly
The idea of safety stock is similar to the idea of a reorder point, which is the stock quantity at which you will generate a new purchase order for that product. A reorder point can be the same as your safety stock number, but it’s usually higher to factor in the lead time.
Some numbers you’ll want to take into account as you decide on a safety stock level are: average daily sales and the daily average that product used in work orders (if applicable), as well as the lead time. but for this article, we’ll keep things simple by calculating based on two weeks of extra demand (14 days).
Since the average daily sales for the Ghost are 2.11 (as calculated earlier on this page), that means the safety stock for Ghost is about 14 x 2.11 = 29.54.
Or 30 if you round the number up.
After all, nobody really orders 0.54 pairs of glasses.
[We’ve also written a more detailed article on safety stock, if you’d like to calculate it based on lead-time demand.]
Putting the reorder point formula together
Now that we’ve got all of the Archon Optical numbers down, we’re ready to put together a reorder point for the Ghost.
This means that, once the quantity on-hand for the Ghost glasses hits roughly 40 or 41, the people at Archon Optical know to put in another purchase order for more of the product. Because they’ve built an average delivery lead time into the reorder point, the extra Ghost glasses should arrive before Archon ever dips below the amount of safety stock.
However, even if there are production shortages or delays in shipment, Archon Optical’s safety stock ensures that they can continue to sell the Ghost for two weeks before they run out of stock.
Set a basic reordering reminder in a spreadsheet
Reorder points are incredibly powerful for keeping your business running smoothly. It’s one thing to understand the concept, but they’re no use to you if you aren’t set up to reorder in a timely manner.
If you’re a spreadsheet user, you can use conditional formatting for the quantity value of specific cells. It’s a bit of work up front because you’ll have to set it up for each individual cell, but you can set Excel or Google Sheets so that cells turn red the moment they dip below your reorder point, which will warn you when you need to start on a new purchase order.
Reorder faster with inFlow
Unlike spreadsheets, inFlow was designed specifically for working with inventory, so you’ll already have all the quantity and reorder point fields built into the program. This already saves our customers a lot of setup time.
inFlow also takes things a step further with a Reorder Stock window, which identifies which products need reordering, and creates new purchase orders with just one click.