Stock to sales ratio: a monthly check on inventory levels
Compare the inventory you start a month with against what you sell in it, read the result by category, and use it to set the closing stock an open-to-buy budget depends on.
Last updated October 31, 2026
The stock-to-sales ratio compares the inventory you hold at the start of a month with the sales you make during that month. A result of 3.0 means you began the month holding three times what you sold in it. The figure is a quick test of whether a store, or one category inside it, carries stock in proportion to the business it does.
Both sides must use the same basis: inventory at retail against sales at retail, or inventory at cost against sales at cost. Numbers below are fictional worked examples.
Stock to sales ratio formula
Stock-to-sales = inventory value at the start of the month ÷ sales for that month
Retail planners take the opening figure on the first day of the month. The US Census Bureau's national series, described on its definitions page, uses end-of-month inventory against monthly sales instead, read as the number of months of inventory on hand. Either convention works for your own store as long as you keep it the same every month.
How to calculate stock to sales ratio
- Choose the scope: the whole store, one department or one category.
- Value the stock in that scope on the first day of the month. A count at ticket price gives the retail figure; your stock records at cost give the cost figure.
- Total the sales for that scope over the month, on the same basis. Retail sales are the till total before tax; cost sales are the cost of what sold.
- Divide the stock value by the sales total.
- Record the result beside the month and the scope, and repeat on the first of every month.
The arithmetic is simple; the work is in step 2. A monthly stock to sales ratio is only as good as the stock figure behind it. A rolling count, a section at a time, keeps the opening figure close to true.
Stock to sales ratio example
The table shows two fictional categories across three months, both at retail.
| Month | Category | Opening stock | Sales in month | Ratio |
|---|---|---|---|---|
| March | Giftware | $24,000 | $8,000 | 3.0 |
| April | Giftware | $27,000 | $6,000 | 4.5 |
| May | Giftware | $30,000 | $7,500 | 4.0 |
| March | Candles | $9,000 | $6,000 | 1.5 |
| April | Candles | $8,000 | $5,000 | 1.6 |
| May | Candles | $10,000 | $8,000 | 1.25 |
Giftware's stock climbed every month while sales dipped in April, so the ratio rose from 3.0 to 4.5 and settled at 4.0. The buyer kept receiving goods through a slow month. Candles stayed between 1.25 and 1.6, with stock moving in step with sales. The two categories need different reactions, which is why the stock to sales ratio by category tells you more than one store-wide figure.
What is a good stock to sales ratio?
There is no universal figure. A jeweler holding slow, high-value pieces runs a high ratio and stays healthy; a bakery counter runs close to zero. Judge each category against three things.
- Its own history. The same month last year is the fairest comparison for a seasonal category. A ratio that climbs for three months in a row while sales hold steady means stock is building.
- The sales pattern ahead. A high ratio at the end of October, before the holiday season, is deliberate. The same ratio at the end of January is not.
- Its margin and shelf life. Perishable and fashion stock cannot carry a high ratio for long. Durable, slow-moving stock with a wide margin can.
A high value suggests stock is running ahead of demand: a slow month, over-ordering, or goods that have stopped selling. The dead stock review is the next step when the ratio keeps rising. A low value suggests stock is thin relative to sales. That may be efficient, or it may mean empty shelves and lost sales, so check the shelf first.
Stock to sales vs inventory turnover
Turnover counts how many times average stock sold through in a year. The stock-to-sales figure describes one month's starting position. When the ratio is calculated consistently and stock levels are reasonably stable, the two are linked:
Annual turnover ≈ 12 ÷ average monthly stock-to-sales
Giftware's three-month average above is about 3.8, which points to roughly 3.2 turns a year if the pattern held. Candles average about 1.45, pointing to roughly 8.3 turns. Shopify's stock-to-sales guide makes the same connection. The approximation breaks down when opening stock swings sharply month to month, so calculate turnover from its own inputs when you need an annual figure; the turnover guide walks through them.
Months of supply vs stock to sales
The ratio reads as months of supply at the current rate of sale, which is why a result of 3.0 can be spoken of as three months of stock. Coverage in days, from the coverage calculator, does the same job for one product in units rather than one category in dollars. Use days for individual reorder decisions and the ratio for the category view.
How the ratio feeds an open-to-buy plan
An open-to-buy plan needs a planned closing stock for each month, and the ratio is how buyers set it. If the candle category sells well at a ratio near 1.5 and next month's planned sales are $8,000, the planned opening stock for that month is about $12,000. That becomes this month's planned closing stock, and the purchase budget follows from it. The OTB guide shows the rest of the calculation, and the free calculator runs it from the four inputs.
How to lower stock to sales ratio
A rising ratio comes down in one of two ways: sell more from the stock you hold, or bring in less. In practice, buyers do both.
- Cut incoming orders for the category until the ratio returns to its usual range. The open-to-buy budget does this automatically if the planned closing stock is held.
- Check sell-through by product with the sell-through calculator to find which lines in the category are not moving.
- Mark down the stock that has stopped selling, following a plan rather than a panic; the markdown strategy guide covers the sequence.
- Move stock between stores if one location sells the category faster than another, or return goods to the supplier where terms allow.
Tracking the ratio in a small store
Two numbers a month per category are enough: the sales total and a stock value on the first of the month. Sales come from the register or your sales records; the stock value comes from a count at ticket price or from stock records that carry a value. Keep them in a sheet with one row per month and one column per category.
headoffis Analytics shows recorded sales value and units for the last 7, 30 or 90 days, by location, with a CSV export of daily totals, and a current stock snapshot in units. It does not value stock, so the ratio needs your own stock value figure. The free calculators at /tools work without an account, use only the numbers entered and save nothing.