Buffer stock to avoid stockouts. The Safety Stock Calculator takes maximum daily sales (units), average daily sales (units), maximum lead time, average lead time and returns safety stock (units) plus days of average sales covered. Results update as you type, and the formula is shown under the result so you can repeat it in your own spreadsheet.
Online and retail margins are decided by the costs that are easy to forget: fees, shipping, returns, storage and advertising. Fill in every line, even with an estimate, before deciding what to sell and at what price. Use the worked example below to check the maths against your own figures.
How the Safety Stock Calculator works
Safety stock protects against the two things that go wrong at once: a demand spike and a late delivery. This formula sizes the buffer for the worst case you have seen.
Worked example
With the example values (maximum daily sales (units) of 60, average daily sales (units) of 40, maximum lead time of 12 days, average lead time of 8 days), the safety stock (units) is 400; days of average sales covered 10 days. Change any figure above and the result updates immediately; use Copy results to paste the summary into a note or email.
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Frequently Asked Questions
How is safety stock (units) calculated?
safety stock = maximum daily sales × maximum lead time − average daily sales × average lead time.
Which figures do I need?
Maximum daily sales (units), average daily sales (units), maximum lead time, average lead time. Take them from the same period and the same set of accounts or reports so the ratio is consistent, and check the example values as a guide to the units expected.
Which fees should I include?
Every fee your platform or provider charges on a sale: commissions, payment processing, fulfilment, storage, advertising and the expected cost of returns. Fee schedules change, so check the current rate card.
