SellersCalc

Inventory math

Stock to Sales Ratio Calculator

How many dollars of inventory you hold for every dollar of monthly sales: the retail buyer’s early-warning gauge.

Stock-to-sales ratio = inventory value on hand ÷ monthly sales value. It tells you how many months of stock you are sitting on at the current sales pace, using matching valuations for both sides. Holding $60,000 of inventory against $40,000 of monthly sales gives a ratio of 1.5, a month and a half of cover. Retail buyers typically want 1.0–2.0 for steady goods; ratios creeping past 3 signal over-buying, while ratios under 1 on long-lead-time products signal stockouts ahead. The unit-level twin of this dollar gauge is the weeks of supply calculator, and the annualized speed reading is inventory turnover. Enter your two values to read the gauge.

Stock to Sales Ratio Calculator — your numbers

Stock-to-sales ratio

1.50

Months of cover

1.50

Estimate only. Results reflect exactly the numbers you enter — verify against your own accounting before making pricing decisions.

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Worked examples

Balanced assortment

Inventory value on hand $60,000.00
Monthly sales value $40,000.00
Stock-to-sales ratio 1.50
Months of cover 1.50

A 1.5 ratio: six weeks of cover, comfortable for most replenishment cycles.

Post-holiday hangover

Inventory value on hand $90,000.00
Monthly sales value $25,000.00
Stock-to-sales ratio 3.60
Months of cover 3.60

Sales slowed but stock did not: 3.6 months of cover and cash locked up.

The stock to sales formula. The stock to sales ratio formula is inventory value on hand ÷ sales for the same period, with both sides at the same valuation. The metric is also called the inventory to sales ratio — identical math, different name — and here is how to calculate it in practice: take beginning-of-month inventory (retail buyers use BOM by convention), divide by that month’s sales, and read the result as months of cover. $60,000 of stock over $40,000 of monthly sales is 1.5. Flip the division and you get the sales to stock ratio, the same gauge upside down, where higher means leaner.

Frequently asked questions

What is a healthy stock-to-sales ratio?

For most e-commerce assortments, 1.0–2.0 is comfortable: enough cover to avoid stockouts without drowning in stock. The right number scales with lead time: a store restocking from overseas in eight weeks reasonably runs 2.0–2.5, while one with week-long domestic resupply can live near 1.0. Watch the trend as much as the level; a climbing ratio is the earliest over-buying alarm.

Should I value inventory at cost or at retail?

Either works, as long as both sides match. Retail-value inventory ÷ retail sales, or cost-value inventory ÷ COGS: never mix them, or your margin silently inflates or deflates the ratio by 30–50%. Most merchants find cost-to-COGS easiest because both numbers come straight from their accounting system without a markup assumption.

How is this different from days or weeks of supply?

Same idea, different units and altitude. Stock-to-sales expresses cover in months of dollars and is usually computed store-wide or per category for buying budgets; weeks of supply is usually computed per SKU in units for reorder timing. A ratio of 1.5 is roughly 6.5 weeks of supply. Buyers plan open-to-buy with this ratio, then execute per SKU with weeks of supply.

My ratio jumped after a slow month — should I panic?

One bad month moves the ratio mechanically because sales is the denominator; that alone is not a crisis. It becomes one if the level persists: two or three months above your normal band means the buying plan assumed demand that is not arriving. Respond by pausing reorders on the heaviest categories and pulling forward promotions, not by panic-liquidating after a single soft month.

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