twelfth · Free tools
Six calculators, a spreadsheet and connected examples. Free to use without signing in; all example figures are illustrative.
Change the example figures to see each result update here. Try the connected concepts to understand what the number leaves out, or use the spreadsheet for a list of products.
Calculate weeks of cover
Weeks of cover = usable units on hand ÷ expected units sold per week
At this sales rate, stock lasts 2.00 weeks. Cover is only as reliable as the expected weekly sales rate. A stockout or promotion can distort that rate.
Another example: If supplier delivery takes longer than current stock cover, check the reorder point and confirmed stock on order. Read Replenishment →
Check a replenishment threshold
Reorder point = expected demand during lead time + safety stock
The stock position is 10.00 units below the reorder point. A gap below the reorder point signals a review; it is not automatically the quantity to order.
Another example: A reorder point can flag action even while stock appears to cover near-term sales. Read Weeks of cover →
Calculate sell-through
Sell-through = units sold ÷ (opening stock + receipts) × 100
30.0% of the units available in this period sold. Whether sell-through is healthy depends on how far through the selling period you are.
Another example: At week ten of a twelve-week season, low sell-through may prompt a price test; at week two, it may be too early. Read Markdown →
Calculate a markdown
Price reduction = (original price − new price) ÷ original price × 100
Gross profit per unit changes from $50.00 to $30.00. The margin result is per unit. It does not predict how many extra units a lower price will sell.
Another example: Compare sell-through before and after a price test to see whether the line actually moved faster. Read Sell-through →
Calculate a price index
Price index = competitor price ÷ your price × 100
The competitor is 10.00% cheaper on this matched item. On this convention, 100 is price parity; below 100 means the competitor is cheaper. Check the match first.
Another example: A 12-pack and a 24-pack are not a fair price match. Check the exact product, size, seller and date. Read Matched SKU →
Calculate GMROI
GMROI = gross margin earned ÷ average inventory at cost
That is $3.00 of gross margin per $1 of average inventory at cost. GMROI compares gross margin earned with average inventory at cost over the same period.
Another example: Two lines can earn the same margin dollars while one ties up much more stock. Compare their roles before removing either. Read Range review →
A single metric rarely settles a retail decision. These examples connect the calculation to the next question a buyer or planner would ask.
A product has 30 usable units on hand and is expected to sell 15 each week. A supplier takes two weeks to deliver. The team holds 10 safety units and has nothing confirmed on order.
Step 1
30 ÷ 15 = 2 weeks of cover.
The stock could run out just as a normal delivery arrives, before allowing for a delay or an unexpected rise in demand.
Step 2
15 × 2 + 10 = 40 units at the reorder point. Stock position is 30, so the gap is 10 units.
Review the order now. The 10-unit gap does not account for the next order cycle, case packs or minimum order quantities.
Before ordering, check whether the weekly forecast was depressed by an earlier stockout and whether any unrecorded delivery is due.
Concepts that change the reading
A line began the period with 300 units, received another 100 and sold 120. Its original price is $100, proposed price is $80 and unit cost is $50.
Step 1
120 ÷ (300 + 100) = 30% sell-through.
Thirty percent is a pace measure. It needs the date in the season and the remaining stock to mean anything.
Step 2
($100 − $80) ÷ $100 = 20% price reduction. Gross margin moves from 50% to 37.5% per unit.
Each unit would earn $30 gross profit instead of $50. Estimate the likely extra units and the effect on nearby lines before making the cut.
A clearance decision also needs an exit date and a view of whether the new price draws sales from another line in the range.
Concepts that change the reading
Your price for an item is $20 and a competitor lists it at $18. The item earned $12,000 gross margin over the year on $4,000 average inventory at cost.
Step 1
$18 ÷ $20 × 100 = 90 on the competitor-price-over-your-price scale.
The competitor is 10% cheaper if the article, pack size, seller and observation date truly match.
Step 2
$12,000 ÷ $4,000 = 3.0 GMROI for the year.
The line earned $3 gross margin per $1 of average inventory at cost. That does not, by itself, justify matching the lower price.
Check the intended price position, margin floor and how long the gap has existed before proposing a price move.
Concepts that change the reading
The workbook has six tabs and rows ready for your own products. Open it in Excel or import the .xlsx file into Google Sheets.
Check role, sales, margin, availability and shopper need before adding or removing a line. Set a date to test whether the change worked.
Need the meaning behind a measure? Browse the retail glossary.
Want to run these checks across a whole category with your own data? Show us the decisions your team is working through.