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Inventory Turnover Calculator

Inventory turnover measures how many times per year you sell through and replace your stock. Higher turnover means inventory moves fast and ties up less working capital. Lower turnover means slow movers, dead stock, and the carrying cost that comes with them. This calculator shows both — turnover against industry benchmarks, and what excess inventory is costing you in dollars per year.

Not sure where to find these numbers in your books? See where to find them in QuickBooks, Wave, or your accountant's report.

Choose an industry to see how your numbers compare to typical businesses like yours.

Trailing 12 months COGS from the income statement.

(Beginning inventory + ending inventory) / 2 if you have both. Period-end inventory works too — slightly less smooth.

Fill in industry, annual COGS, and average inventory to see your turnover ratio and what it's costing in carrying cost.

The formula

Inventory Turnover = COGS / Average Inventory
Days Inventory Outstanding (DIO) = 365 / Inventory Turnover

A turnover of 8 means you cycle through your inventory eight times per year. Equivalently, DIO of 45 means inventory sits on shelves about 45 days before becoming a sale.

Use COGS, not revenue, in the numerator. Inventory is valued at cost on the balance sheet, so cost-to-cost is the right comparison. Some sources use revenue / inventory; that produces a different (less accurate) ratio that conflates margin with turnover.

Why turnover matters

Inventory ties up cash. Every dollar in inventory is a dollar you can't use for payroll, marketing, expansion, or paying yourself. The carrying cost is real:

  • Financing cost: roughly 10% per year for the typical small business (line of credit rate or opportunity cost)
  • Storage cost: warehouse space, insurance, handling — often 2-5% per year
  • Obsolescence: aging stock loses value, especially in fashion, tech, or perishable goods
  • Shrinkage: theft, damage, miscount — typically 1-2% per year

Combined, total carrying cost typically runs 15-25% of average inventory value per year. The calculator above uses 10% as a conservative lower bound (just the financing cost) — your real total is probably higher.

Industry benchmarks vary enormously

There's no universal "good" turnover number. It depends on what you sell:

  • Restaurants: 25-40x per year (DIO 9-15 days) — fresh ingredients can't sit
  • Grocery and convenience: 15-25x (DIO 15-25 days)
  • Fashion / fast-moving consumer goods: 6-12x (DIO 30-60 days)
  • General retail: 4-8x (DIO 45-90 days)
  • Manufacturing: 4-6x (DIO 60-90 days) — work-in-progress and finished goods both count
  • Industrial / heavy equipment: 2-4x (DIO 90-180 days) — long sales cycles, large items

A construction supply company with 4x turnover is healthy. A restaurant with 4x turnover is in serious trouble. The benchmark in the calculator above adjusts for your industry.

Why is your turnover lower than benchmark?

The pattern is usually one of these:

  1. Slow-moving SKUs accumulating. The 80/20 rule applies hard to inventory. A handful of items sell fast; the rest sit. Aggregate turnover looks fine until you break it down by SKU.
  2. Forecasting based on peak season. Purchasing patterns set during the busy season carry into slower periods, building dead stock.
  3. Vendor minimums or volume discounts. Buying 6 months of stock to get the discount looks smart on a per-unit basis but kills turnover. Often the financing cost on the excess wipes out the discount saving.
  4. SKU proliferation. Adding sizes, colors, and variants dilutes velocity per SKU. More SKUs almost always means more dead stock.
  5. Returns and damage sitting in inventory. Unsellable stock that hasn't been written off looks like inventory but isn't.

What to do about slow turnover

This week

  • Pull an inventory aging report — flag anything that hasn't moved in 90+ days
  • Calculate sell-through by SKU; identify the worst 20%
  • Make a write-off list of clearly unsellable stock and talk to your CPA

This month

  • Discount aging stock aggressively to clear — recovering 50-70% of cost beats carrying for another year
  • Review purchasing patterns — are orders driven by actual sell-through or autopilot?
  • Set min/max levels per SKU based on sales velocity
  • Stop buying slow movers entirely until existing stock clears

This quarter

  • Audit SKU count — every variant should justify its existence with sales
  • Negotiate smaller, more frequent orders with key vendors (often possible even when minimums are stated)
  • Implement a basic inventory management system if you're still on spreadsheets
  • Consider whether vendor-managed inventory or drop-shipping fits any of your product lines

The trap of looking too efficient

Higher turnover isn't always better. Stockouts cost money — lost sales, expedited shipping, customer dissatisfaction, missed manufacturing windows. The optimum is the industry healthy range, not the maximum possible.

If your turnover is dramatically above industry — say, 40x for a retail business when industry is 4-8x — you're probably running too lean. Track stockout rate alongside turnover; if you're losing sales because items are out of stock, the carrying-cost savings aren't worth it.

FAQ

Should I use period-end or average inventory?

Average is more accurate (smooths out seasonal swings), but period-end is simpler and often what's available. For benchmarking, check what your data source uses. If you have monthly inventory snapshots, average across the year is most accurate.

What about service businesses with no inventory?

Inventory turnover doesn't apply. Service businesses should focus on DSO (receivables turnover) and labor utilization instead.

What about work-in-progress for manufacturers?

Include WIP in inventory. From a working capital perspective, WIP ties up cash exactly the same way finished goods do — sometimes more, because WIP can't be sold until completion. The calculator's "average inventory" should be raw materials + WIP + finished goods.

Does the carrying cost actually equal 10%?

For most small businesses, total carrying cost is 15-25% of inventory value annually (financing + storage + obsolescence + shrinkage). The calculator uses 10% as a conservative lower bound based on financing cost alone. If you have a clear sense of the other components, your real carrying cost is probably higher than what the calculator shows.