Choose one item that has a frequent need and would cause problems if it ran out. This could be labels, gloves, cleaning supplies, etc. On a piece of paper or a computer note, next to the name of the item, write down the quantity that you have on hand, what the normal usage rate is over a short time period, and the lead time of a new order. Now you have the beginnings of a reorder decision. You are not trying to figure it out from memory. You are looking at usage, quantity on hand, and lead time.
A lot of times, a stockout occurs because you did not place an order when you should have. The solution to this is to determine your reorder point ahead of time. If your supply of something normally lasts 10 days and it takes 4 days to get a new order, don’t wait until there are 1 or 2 days left. Start thinking of the lead time as a feature of the item. In other words, there is no item that is just a quantity on a shelf. There is also a lead time associated with the item that dictates when it should be reordered.
A 15-minute exercise can help this become clear. Take 5 minutes to physically count the quantity of one item that moves frequently. Take 5 minutes to estimate how long that quantity will last at a normal usage rate. Take your last 5 minutes to decide what is the latest reorder point for that item and write 1 sentence about why you made that decision. This exercise works because it forces you to think about supply planning as a repetitive decision. You are not trying to anticipate every problem. You are trying to develop a cadence of when to take action.
Sometimes you will struggle with this exercise because of irregular demand. Some days it does not take very much, other days it does. One of the mistakes that a lot of people make in this situation is to over order. This just creates another problem of having too much inventory on hand that takes up valuable space and attention. Instead, the solution is to really think about the demand over the last week or month. Was the demand really irregular or did you just choose to ignore the pattern? Did the spike in demand occur at a regular interval? Did the late arrival of one shipment skew your thinking? A few minutes of postmortem analysis after every reorder decision will help refine your timing more than a stack of notes.
One of the most important things you can do to develop your reorder timing is to compare your expectations to your results. Maybe you thought something would last one more week but it actually ran out much faster. Maybe you ordered something ahead of time and it actually took longer than you thought. Both of those outcomes can teach you something. Supply planning is a process of refinement. The goal is not to become 100% accurate overnight. The goal is to develop a critical eye for inventory usage, lead time, and the point at which procrastination becomes a stockout.