™AutoFire™ tools / Inventory & profit
Free Dealership Inventory Turnover Calculator
Calculate vehicle unit turns, annualized inventory turnover, and current days supply from your dealership's sales and stock counts.
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For informational use only. Use consistent unit counts, inventory scope, and reporting periods. Annualized turnover and days supply are pace estimates, not sales forecasts.
How to use this tool
- 1Choose a reporting period and enter units sold, beginning stock, and ending stock for the same inventory segment.
- 2Enter current available stock to estimate days supply at that period's sales pace.
- 3Compare periods consistently and inspect aged units before changing your buying plan.
How the result is built
Average inventory = (beginning + ending units) ÷ 2. Period unit turns = units sold ÷ average stock. Annualized turns multiply by 365 ÷ period days. Current days supply = current stock ÷ average daily unit sales.
An example from the lot
Sell 18 units in 30 days with 45 units at the start and 39 at the end. Average inventory is 42, annualized turns are about 5.21, and 42 units currently in stock imply 70 days supply at the same sales pace.
A practical guide to this calculation
Inventory turn and days supply answer related but different lot-management questions. Turns compare sales with average stock over a reporting period. Days supply compares today's stock with a recent sales pace. This calculator keeps vehicle units consistent across both views, helping an inventory manager review a segment without mixing retail revenue and acquisition cost.
Worked example using the starting values
Sell 18 units in 30 days with 45 units at the start and 39 at the end. Average inventory is 42, annualized turns are about 5.21, and 42 units currently in stock imply 70 days supply at the same sales pace.
- Average units in stock
- 42.00
- Unit turns during period
- 0.43
- Annualized unit turns (365 days)
- 5.21
- Days per inventory turn
- 70.00
- Current days supply at period sales pace
- 70.00
This example remains here when you change the interactive fields above. Your scenario results are shown inside the tool and can be downloaded as a CSV.
Keep the inventory segment consistent
Choose one segment, such as retail-ready used vehicles, and use it for every stock count and sale. Decide how pending, wholesale, consignment, and unavailable units are treated before comparing periods. A change in what counts as inventory can move the result even when the underlying sales process did not improve.
The beginning and ending counts form a simple two-point average. That is convenient for a period review but can miss a large mid-period purchase or disposal. If your stock changed sharply during the period, compare this estimate with a more detailed average from your own daily inventory records.
Read period turns and annualized turns separately
Selling eighteen units against an average of forty-two gives about 0.43 turns during that specific period. Annualization scales the ratio using 365 divided by the entered number of days. It makes periods easier to compare mathematically, but assumes the recent pace continues and should not be presented as a sales forecast.
Days per turn divides period days by the period-turn ratio. It describes the average stock-to-sales relationship, not the actual age of each sold vehicle. Keep an aging report beside the result: one slow unit can be hidden inside a reasonably fast overall ratio.
Use current days supply to organize a buying discussion
Current days supply uses the separate current-inventory input. It can differ from days per turn because today's stock need not equal the period average. In the example, forty-two current units divided by 0.6 daily unit sales gives seventy days supply. Changing current stock alone should change supply without changing historical turns.
If there were no sales, neither days per turn nor days supply has a finite value. The calculator displays those results as undefined rather than implying that stock will sell in zero days. Review the period length, stocking decisions, merchandising, and unit-level holding costs before deciding what to purchase next.
Common questions
Is this the accounting inventory-turnover ratio?
This page calculates vehicle unit turns. An accounting ratio often uses cost of goods sold and average inventory at cost. Those are different inputs. Do not divide retail revenue by acquisition-cost inventory and label that result equivalent to this unit-based measure.
Which period length should I enter?
Use the actual number of days covered by the sold-unit and stock figures. A calendar month can have a different number of days from a fixed thirty-day report. Keep the method consistent when comparing similar segments and periods.
Does a high turn rate always mean inventory is healthy?
The ratio alone cannot establish that. Gross profit, availability, stocking depth, aging, and the sales mix still matter. Review turns with unit profit and holding costs instead of treating one number as a universal target for every dealership.
Method and reference material
- Dealer Institute: dealership financial measures
- Shopify: inventory-turnover and retail-math definitions
Formula and example reviewed October 29, 2026. For another task, browse the free dealership tools directory.