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Safety stock and reorder point calculator

Built on your total lead time, not the supplier's quote. Five inputs, and you see three numbers: your safety stock in units, the reorder point that keeps you in stock, and the one your spreadsheet probably uses. No email, no signup.

AY
Anand Yadav · Founder, ReccordSOP
·Last reviewed August 4, 2026

Five numbers, all in days except the first. Everything is calculated in your browser.

Use a 30-60 day average for this SKU. Decimals are fine.

The production + ship time on the quote or the last PO confirmation.

For your actual shipping mode. Sea freight from Asia is typically 25-40; air is 5-10; domestic ground 2-5.

Dock to sellable. Most 3PLs quote 1-3 business days; peak season runs longer.

How many days of demand you want as a cushion. 7-14 for steady A-SKUs; more if demand or the supplier is volatile.

The reorder point formula

A reorder point is the stock level that triggers your next purchase order. The formula has two halves:

Reorder point = (average daily demand × total lead time in days) + safety stock

Safety stock = average daily demand × days of cover

The first half covers what you will sell while the order is in transit. The second is the buffer that absorbs a demand spike or a late shipment. This calculator sets safety stock in days of cover rather than the statistical z-score method, because days of cover is a number an operator can defend in a meeting and revise on the spot. Seven to fourteen days suits a steady A-SKU. Push it higher when demand swings, when the supplier has slipped before, or when the lead time itself is long, since a long pipeline gives you less time to react to any of it.

The formula is fine. The lead-time input is what fails.

Every reorder point formula is the same multiplication: daily demand times lead time, plus a buffer. What separates brands that stay in stock from brands that do not is one input. The supplier's quoted lead time covers production. Your money is on the shelf only after freight, customs, and your 3PL's receiving queue, and that total is routinely two to four weeks longer than the quote. A reorder point built on the quote is not wrong math, it is right math on a wrong number, and it fires the purchase order weeks late every single cycle.

FAQ

The stock level that triggers a new purchase order for a SKU. The formula is demand during lead time plus safety stock: your average daily sales multiplied by the days it takes a new order to become sellable stock, plus a buffer. When on-hand inventory drops to that number, you order.

Your total lead time, not the supplier's quote. The quote covers production and sometimes shipping. It leaves out freight and customs for your actual shipping mode and receiving at your warehouse or 3PL. Measure it from your last two purchase orders: PO date to the stock going sellable. If the last two POs disagree, use the slower one.

Safety stock equals your average daily demand multiplied by the days of cover you want to hold. Sell 40 units a day and want 10 days of cover, and your safety stock is 400 units. The statistical alternative multiplies a service-level z-score by the standard deviation of demand over lead time, which is more precise in theory and, in practice, is precision applied on top of a lead-time figure most brands have never measured. Fix the lead time first.

This calculator uses days of cover, which is deliberately simpler than the statistical z-score formulas: 7 to 14 days of demand for steady A-SKUs, more when demand is volatile, the supplier has slipped before, or the lead time is long. If you want the fuller treatment with variability math, an inventory tool can layer it on later. Most stockouts are caused by a wrong lead time, not by an unsophisticated buffer.

Monthly for your top-revenue SKUs, and immediately when a product's velocity shifts hard or a supplier's lead time changes. A reorder point is a snapshot of one moment's demand and lead time. Set once and never revised, it fails quietly: the trigger still fires, just too late.

No. Everything is calculated in your browser. Nothing is collected, nothing is sent anywhere.

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