Free tools / Reorder point

Reorder point and order quantity calculator.

Two questions for every stocked item: at what level do I reorder, and how many do I order? Most calculators assume your supplier is never late. This one lets you say how late they run.

No sign-up. Nothing you type leaves your browser.

WHEN TO REORDER

units
The standard deviation of daily sales. If you do not know it, a rough guide is a quarter of the gap between a busy day and a quiet day. Use 0 if sales are steady.
days
days
If deliveries usually land within two days either side of the promise, use 2. Use 0 for a supplier who is never late.
%
The share of reorder cycles you want to get through without running out. Higher costs more stock: going from 95 to 99 adds roughly two fifths to your safety stock.

HOW MUCH TO ORDER

Your time raising and receiving it, plus any fixed delivery charge.
% of its cost
Storage, insurance, damage and the money tied up. 15% to 30% is a common range.
REORDER WHEN STOCK FALLS TO

ORDER THIS MANY EACH TIME

The reorder point

You need enough on the shelf to cover what you will sell while the new stock is on its way, plus a cushion for the days that do not go to plan. That cushion is safety stock.

reorder point = (daily sales × lead time) + safety stock

Safety stock, when both sales and deliveries wobble

The usual formula only allows for uneven sales. In practice a late delivery empties a shelf at least as often as a busy week does, so this calculator allows for both:

safety stock = z × √( lead time × sales swing² + daily sales² × lead-time swing² )

z comes from the service level you choose: 1.28 for 90%, 1.64 for 95%, 2.33 for 99%. Set either swing to zero and that half of the formula drops away.

The economic order quantity

Order often and you pay for a lot of orders. Order rarely and you pay to store a lot of stock. The economic order quantity is the size where those two costs are equal, which is also where their total is lowest.

EOQ = √( 2 × yearly demand × cost per order ÷ yearly holding cost per unit )

Treat it as a starting point. Pack sizes, minimum orders, price breaks and shelf life all have a say, and the total cost curve is flat near the bottom, so rounding to a full case costs very little.

Questions

Reorder against what number: on hand, or available?

Available. On hand counts stock that is already promised to orders you have accepted. If you reorder against on hand, you reorder late.

What if I have more than one location?

Work it out per location, using that location’s own sales and the lead time to get stock there.

My sales are seasonal. Does this still work?

Use the daily sales for the season you are heading into, not the yearly average, and work it out again when the season turns.

Is my data sent anywhere?

No. The sums are done in your browser.

OrbisVendor lets you set a reorder point on a product. Working one out from demand and lead time is not part of the product yet. That is why this tool stands alone.

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