How the Sell-Through Rate Calculator works
Sell-through rate (STR) measures how much of the inventory you had available to sell during a period actually sold. It is a standard retail and e-commerce metric used to judge how well a product, style, or SKU is moving before deciding on reorders, markdowns, or promotions.
The formula
For a starting count of beginning inventory, any units received (restocked or newly delivered) during the period, and the units sold over that same period, the sell-through rate is:
STR (%) = Units Sold ÷ (Beginning Inventory + Units Received) × 100
The denominator — beginning inventory plus units received — is the total number of units you had a chance to sell during the period. STR simply expresses units sold as a percentage of that total. The calculator also reports units available, units remaining unsold, and a weekly pace (the rate divided by the number of 7-day weeks in the period), which assumes sales were spread roughly evenly across the period.
Worked example
Say you started a 30-day period with 500 units in stock, received 200 more mid-period, and sold 420 units by the end. Units available = 500 + 200 = 700. Sell-through rate = 420 / 700 × 100 = 60%. That leaves 280 units unsold, and since 30 days is about 4.29 weeks, the weekly pace works out to roughly 60% / 4.29 ≈ 14.0% per week.
Reading the result
- Higher sell-through means more of the available stock moved — useful for spotting strong performers worth reordering before they sell out.
- Lower sell-through can flag overstock, weak demand, or pricing that needs adjustment, especially if the rate stays low well into a selling season.
- Weekly pace lets you compare periods of different lengths — a 30-day launch and a 90-day season — on the same footing.
What this calculator does not do
It is pure arithmetic on the figures you enter: it does not know your product category, season, or markdown calendar, and it cannot tell you whether a given rate is "good" for your business. There is no single universal benchmark — compare your result against your own category's historical sell-through rather than a fixed number, and treat this as one input alongside merchandising judgment, not a replacement for it.