Stock-to-Sales Ratio (SSR) Formula
How apparel planners calculate the stock-to-sales ratio, illustrative channel-level ranges, and why SSR is the fastest read on whether OTB is balanced.
What Stock-to-Sales Ratio measures
SSR is the monthly dollar relationship between beginning-of-period inventory and sales for that period. Planners use it to calibrate OTB — if SSR is too high, the buy needs to pull back; too low, stock-out risk rises.
SSR = Beginning-of-Period Inventory ÷ Sales for PeriodPlan SSR at the monthly grain of the merchandise financial plan. The ratio varies by season — higher in February when inventory is building for spring, lower in peak months where inventory flows through fast.
Worked apparel example
A DTC brand opens May with $1.1M of BOP at retail and expects $400K in May sales.
SSR = $1.1M ÷ $400K = 2.75
Lean — under 3, the lean end of the illustrative DTC range below. If sell-through accelerates, stock-out risk. If it slows, inventory ages. The planner watches Week-1 and Week-2 reads against plan and adjusts the June receipt flow accordingly.
SSR of 2.8 is lean. Risk of stock-out if lead times slip.
Illustrative planning ranges
Illustrative reference points, not a published benchmark — set targets from your own history.
Failure modes we see
SSR calculated only when the plan is built. The ratio locks in at plan submission. Actuals drift; SSR drifts; nobody re-computes until the next plan cycle. The drift is only found at hindsight.
How RetailNorthstar handles SSR
SSR recomputes weekly at department and class grain against the live inventory position. When drift crosses a threshold, the system surfaces the recommended OTB adjustment — pull back future receipts or accelerate them.
Related formulas
- Open-to-Buy — SSR is the primary calibration for OTB
- Weeks of Supply — the weekly version
- Receipt Plan — the flow that balances SSR
See SSR live by department — with the OTB adjustment recommendation attached.
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