Data-Driven Purchasing for Shops: Buy What Sells

Purchasing decisions based on sales data: buy what sells

Many shop owners buy on experience and instinct. That helps, but it isn’t enough when items multiply and prices change fast. Sales data complements experience and reveals what the eye can’t see.

Retail 6 min read

By Nour Aldein Tleti. Updated 7 October 2026.

How do you make purchasing decisions based on sales data?

Start from the actual sales record of each item over a long enough period, and work out how fast it sells and how long the supplier takes to deliver. On that basis, set the order quantity and the reorder point, and cut back on buying slow-moving items. Review these figures regularly, because demand and prices change.

Figures you should know for every item

Sales rate: How many units sell per week or month on average.
Days of cover: How many days current stock will last if sales continue at the same rate.
Lead time: How many days the supplier needs from order to delivery, with a margin for delays.
Margin: The difference between purchase and selling price; a fast item with a thin margin is managed differently from a slow item with a high margin.

Reports that help you decide

Best sellers: The top items by quantity and value, the ones that must never run out.
Dead stock: Items that haven’t sold for a long time and need a promotion, a markdown or a stop on purchasing.
Seasonality: Comparing sales across seasons and occasions such as Ramadan, the Eids and back to school, so you can prepare early.
Stock-outs: Items that ran out and how many days they were unavailable; every day out of stock is lost sales.
Profitability by supplier: Compare item profitability by supplier; the cheapest supplier may be less profitable because of returns or delays.

Considerations for the Syrian market

Price swings: Expecting prices to rise can tempt you to overstock, but that freezes cash, so balance the fear of higher prices against the shop’s need for cash.
Availability of goods: Some items may suddenly disappear from the market, so keep larger safety stock for essentials only.
Pricing in two currencies: Record the purchase price in the actual currency with the exchange rate, so the real margin shows after the rate changes.
Local spending patterns: Sales may rise before occasions or after remittances arrive from relatives abroad, so look for these patterns in your data before building on them.

A data-driven purchasing cycle

01
Pull the sales report
Sales of each item over a period that represents the shop’s normal activity.
02
Calculate the reorder point
Daily sales rate multiplied by the lead time, plus safety stock.
03
Review dead stock
Decide what to do with items that aren’t moving before any new purchase.
04
Issue the purchase order
From the system, using the calculated quantities, adjusted by your experience and the supplier’s information.
05
Compare after the season
Did you sell what you expected? Use the difference to improve the next order.

Classifying items for purchasing decisions

Category	Description	Purchasing decision
Fast-moving essential	High, steady sales	Fixed safety stock and regular orders
Seasonal	High sales in specific periods	Buy early before the season and clear afterwards
Slow but profitable	Low sales and a good margin	Small, frequent quantities
Dead stock	Hasn’t sold for a long time	Stop buying, and promote or clear

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Frequently asked questions

How long a period should the data cover?

At least one normal sales cycle, and for seasonal items it is best to compare with the same period last year.

Can I do this in Excel?

Yes, if you have detailed item-level sales data from your POS. But a system that calculates reorder points automatically saves a lot of time when you have many items.

What if the data contradicts my experience?

Data tells you what happened, and your experience predicts what will happen. Use both, and review the outcome to see which was more accurate in each case.

Can AI be used to forecast demand?

It may help when there is enough clean historical data. Start with the basic reports first; they deliver most of the benefit with less effort.

How do I deal with a supplier who changes prices often?

Record every purchase price with its date, and compare suppliers on the same item regularly; this data strengthens your hand in negotiation.