Replenishment

Reorder point calculator

Free, no email, nothing to install. The one difference from every other calculator is the divisor, and it is the difference that decides whether the answer is right.

Marcus VolstedCo-founder, Restocio Published 6 September 2026Updated 6 September 20264 min read

Your reorder point is the daily sales rate multiplied by your lead time, plus the stock you want left when the delivery lands. The trap is the daily rate. Divide by days elapsed and every product that has ever run out looks slower than it is, so you order less of it, so it runs out sooner. Divide by the days it was actually on the shelf and the number is honest.

Work out your reorder point

Nothing is sent anywhere. The numbers stay in your browser.

Units sold in the period Over whatever window you are looking at

Days it was in stock during that period Not days elapsed. This is the correction.

Lead time in days Order placed to sellable on your shelf

Days of stock you want on arrival Your cushion against a late delivery

Units in stock now

Units already on order On the water or in production

Daily sales rate9 a day

Days of stock left100 days

Reorder point1 170 units

Order this many270 units

You are at or below the reorder point. Ordering later than today means the shelf is empty before the delivery lands.

What the calculator is doing

Three lines of arithmetic, and you can run them yourself.

daily rate = units sold ÷ days in stock
reorder point = daily rate × (lead time + days of cover on arrival)
order quantity = reorder point − stock now − stock on order

With the defaults above: 540 units across 60 in-stock days is 9 a day. A 70-day lead time plus 60 days of cover is 130 days, so the reorder point is 1 170 units. Sitting on 900 with nothing on order, you are 270 short of where you need to be when the deadline arrives.

Why the divisor is the whole thing

Take the same 540 units, but the product was out of stock for 30 of those 90 calendar days. Divide by 90 and the rate is 6 a day. Divide by the 60 days customers could actually buy it and the rate is 9. That is a third of the order gone, on the product that already proved it runs out.

Then it compounds. The smaller order sells through sooner, so next period has fewer in-stock days again, so the measured rate falls further, so the next order shrinks again. Nothing on your dashboard looks wrong at any point. We have written about that loop in full.

What this calculator does not do

It is one product, one moment, and one route. It assumes demand is roughly steady, which is wrong for anything seasonal. It has no view on minimum order quantities, so the answer may not be a quantity your supplier will actually accept. It cannot tell you whether a late delivery needs part of the order flown in, which for importers is often where the money is. And it takes your lead time on trust, when a measured lead time is usually longer than the quoted one.

For a handful of products those limits do not matter and this is genuinely all you need. Past a few hundred, the problem stops being the arithmetic and starts being doing it for every product every week, which is the point at which a spreadsheet stops working.

Common questions

How do you calculate a reorder point?

Multiply your daily sales rate by your lead time in days, then add the stock you want left when the delivery arrives. The daily rate should be units sold divided by the days the product was actually in stock, not days elapsed. At 9 a day with a 70-day lead time and 60 days of cover wanted, the reorder point is 9 times 130, which is 1 170 units.

Is this reorder point calculator free?

Yes, and there is no email form. It runs entirely in your browser and nothing you type is sent anywhere. The formulas are printed on the page as well, so you can rebuild the whole thing in a spreadsheet if you would rather own it.

What is the difference between reorder point and safety stock?

Safety stock is the cushion you want left on the shelf when a delivery lands, and it is one input. The reorder point is the total stock level that triggers an order, which is the demand expected during the lead time plus that cushion. In this calculator, days of stock on arrival is the safety stock expressed in days rather than units.

Why does my reorder point seem too high?

Usually because the lead time is longer than people expect once production, customs and putaway are counted, and those days all multiply against the daily rate. If a 70-day lead time gives a number you cannot afford, the honest options are shortening the lead time, carrying less cover on arrival and accepting more risk, or splitting the order so only part of it travels by the slow route.

Marcus Volsted

Co-founder, Restocio

Marcus co-founded Restocio and works on it daily with a Swedish importer who plans their purchasing in it every working day. Restocio is built in Sweden by two founders, one Swedish and one Danish, and Marcus is the Danish one. Most of the examples on this blog come from that store's real ordering decisions rather than from a textbook. Why we are building it.