Inventory Turnover Calculator UK 2026
— Stock Turnover Ratio & DSI Tool
Use this free inventory turnover calculator to measure how efficiently your ecommerce business turns stock into sales. Calculate your stock turnover ratio, Days Sales of Inventory (DSI), average inventory, SKU-level performance and cash tied up in slow-moving stock — built for Shopify, Amazon FBA, eBay, Etsy, WooCommerce and UK multi-channel sellers.
Inventory Turnover Calculator
Enter your COGS and inventory values below — switch between Standard and Average Inventory modes. Use annual, quarterly or custom periods for management accounts, FBA reviews and cash-flow planning.
Inventory Turnover Ratio Calculator
Calculate stock turnover rate, Days Sales of Inventory (DSI) and stock efficiency rating
Multi-Product Inventory Turnover
Calculate and compare turnover ratios across multiple SKUs or product lines at once
What Is Inventory Turnover?
Inventory turnover, also called the stock turnover ratio, measures how many times a business sells and replaces its average inventory during a period. For ecommerce sellers, it is one of the clearest signals of product demand, buying discipline, cash-flow efficiency and warehouse health.
A healthy inventory turnover ratio means your stock is moving fast enough to generate revenue without excessive cash being trapped in unsold products. A poor ratio usually means too much money is sitting in slow-moving SKUs, old seasonal ranges, dead stock, Amazon FBA storage, or products that need pricing, listing or purchasing action.
2026 Ecommerce Summary
For many UK ecommerce stores, a turnover ratio of 4× to 8× per year is a practical working range, but the right target depends on product category, supplier lead time, seasonality, minimum order quantities and marketplace fulfilment model. Use this calculator with your own COGS and stock value, then compare the result against the category benchmarks below.
Inventory Turnover Formula
The standard inventory turnover formula uses Cost of Goods Sold (COGS) divided by average inventory value. Both figures should be measured at cost, not retail selling price. That is why revenue should not be used in the numerator — revenue includes your margin and will overstate the ratio.
Stock Turnover Ratio Formula
Days Sales of Inventory (DSI) = Period Days ÷ Inventory Turnover Ratio
Inventory Turnover Worked Example
A UK Shopify seller has annual COGS of £120,000. Opening stock was £18,000 and closing stock was £22,000. Average inventory is therefore £20,000.
- Average inventory = (£18,000 + £22,000) ÷ 2 = £20,000
- Inventory turnover = £120,000 ÷ £20,000 = 6.0×
- Days Sales of Inventory = 365 ÷ 6.0 = 61 days
This means the store sold and replaced its average stock holding approximately six times in the year, and each pound of stock was held for about 61 days before turning into COGS.
Use COGS, Not Sales Revenue
COGS usually includes product cost, inbound freight, customs duty, landed cost adjustments and direct packaging costs. It normally excludes marketplace fees, advertising, storage charges, payment processing fees and outbound delivery to customers unless your accountant has specifically classified those costs as direct costs.
How to Use This Inventory Turnover Calculator
-
Choose your calculation period
Use a full year for annual review, a quarter for management accounts, or a custom period for Amazon FBA, seasonal range checks or new product launches. The period affects DSI because DSI converts turnover into days held.
-
Enter your COGS
Use the Cost of Goods Sold figure from your Profit & Loss report. In Xero, QuickBooks or Sage, this is normally shown under Direct Costs, Cost of Sales or Cost of Goods Sold.
-
Enter average inventory
For the most accurate result, use opening inventory plus closing inventory divided by two. The calculator can do this automatically in Average Inventory mode.
-
Review turnover and DSI together
Inventory turnover tells you how many times stock is replaced; DSI tells you how many days stock is held. A ratio of 6× is easier to manage when you also know it equals roughly 61 days of inventory.
-
Compare by SKU, not only company-wide
A business-level ratio can hide a weak product range. Use the multi-product calculator to compare individual SKUs, brands, collections, Amazon ASINs or warehouse locations.
Inventory Turnover Benchmarks 2026 by Ecommerce Category
There is no single official "good" inventory turnover ratio because every product category behaves differently. Fast-moving consumables need rapid turnover; luxury, furniture and specialist products can be profitable with lower turnover. The 2026 benchmark ranges below are practical planning ranges for ecommerce sellers, not statutory tax rules.
| Turnover Result | Typical Meaning | Stock Risk | Suggested Action |
|---|---|---|---|
| Under 2× | Stock is moving slowly or buying is too heavy | High cash tie-up, obsolescence and storage cost risk | Review pricing, promotions, bundles and purchase orders immediately |
| 2×–4× | Acceptable for slow categories but weak for fast retail | Moderate risk; watch ageing stock and margin erosion | Reduce reorder quantities and clear underperforming SKUs |
| 4×–8× | Balanced range for many ecommerce sellers | Generally healthy if stockouts are controlled | Use demand forecasting and reorder points to maintain consistency |
| 8×–12× | Fast-moving stock with strong velocity | Stockout risk if supplier lead times are long | Increase reorder frequency and keep safety stock for best sellers |
| 12×+ | Very fast turnover, common in consumables or low inventory models | Potential lost sales from understocking | Check lost sales, marketplace ranking drops and supplier capacity |
Why Inventory Turnover Matters for Ecommerce Sellers
Cash Flow
Inventory is often the largest current asset in an ecommerce business. Slow stock locks up cash that could be used for ads, supplier deposits, new product launches or VAT payments.
Storage Costs
Amazon FBA, 3PL and warehouse storage costs increase when stock sits for too long. Faster turnover reduces the cost per unit and protects margin.
Gross Margin
Slow-moving stock often needs discounting. Turning stock faster can protect full-price sell-through and reduce clearance markdowns.
Reorder Decisions
DSI helps calculate reorder points. If a SKU has 45 days of inventory and your supplier lead time is 30 days, you have little room for demand spikes.
Balance Sheet Accuracy
Accurate stock value improves your balance sheet, working capital analysis and management accounts. It also helps your accountant identify stock write-down risks.
Investor & Lender Confidence
Stock turnover is a key operational metric for ecommerce valuation, trade finance, supplier credit and lender reviews.
Inventory Turnover for Shopify, Amazon, eBay and Etsy
The same formula applies across every platform, but the operational issues are different. A Shopify store may have more control over fulfilment and product bundles, while Amazon FBA sellers must actively manage stock age and fulfilment-centre fees. eBay and Etsy sellers often have broader SKU ranges, which makes product-level turnover more important than a single business-wide ratio.
| Sales Channel | Inventory Turnover Focus | Accounting Tip | Helpful Internal Guide |
|---|---|---|---|
| Shopify | Product margin, sell-through, returns and reorder timing | Reconcile Shopify payouts separately from COGS and inventory movements | Shopify + Xero Integration |
| Amazon FBA | FBA stock age, storage utilisation, ASIN-level velocity and removal decisions | Use settlement data for sales/fees and FBA inventory reports for stock quantity/value checks | Amazon Seller Accounting Guide |
| eBay | Large SKU catalogues, used/refurbished stock and slow movers | Separate COGS by category or condition if margins vary significantly | eBay Accounting Guide |
| Etsy | Material inventory, handmade lead times and seasonal products | Track raw materials and finished goods separately where possible | Etsy Accounting Guide |
| WooCommerce | Own-store stock control, plugin reliability and warehouse sync | Use SKU mapping to keep accounting software aligned with product catalogue | WooCommerce Accounting Guide |
Amazon FBA Inventory Turnover in 2026
For Amazon sellers, inventory turnover is not just a finance metric — it affects fulfilment cost, storage planning, stock removals and cash flow. Amazon applies monthly storage fees to inventory in fulfilment centres and aged inventory surcharges can apply when units sit for too long. Always check the current Amazon Seller Central fee pages before making FBA storage decisions.
- Track inventory turnover by ASIN, not only by total Amazon account.
- Review stock that has not sold within 90 days, especially seasonal or trend-led products.
- Use DSI to decide whether to replenish, discount, bundle, advertise or remove stock.
- Compare FBA stock quantity to your accounting stock value at every month end.
- Do not let slow-moving FBA inventory hide inside a healthy company-wide turnover ratio.
FBA Fee Check
Because Amazon fee rules can change, link your stock review process to the current Amazon monthly inventory storage fee page and aged inventory surcharge page. Use the calculator above to spot SKUs where DSI is drifting into storage-risk territory.
Inventory Turnover in Xero, QuickBooks and Sage
To calculate inventory turnover correctly, you need reliable COGS and inventory values from your accounting system. The calculator is only as accurate as the numbers entered, so your bookkeeping setup matters.
Xero Inventory Turnover
Xero tracked inventory can record stock quantity, stock value and COGS for tracked items. For ecommerce, many sellers also use integrations such as A2X to post settlement summaries and COGS accurately. Read the Xero ecommerce guide.
QuickBooks Inventory Turnover
QuickBooks Online can track stock products, stock asset values and reorder points on eligible plans. Use Profit & Loss for COGS and Balance Sheet for stock asset value. Read the QuickBooks ecommerce guide.
Sage Inventory Turnover
Sage is useful for stock-heavy businesses that need stronger inventory controls, purchase orders or multi-location reporting. Read the Sage for ecommerce guide.
| Figure Needed | Where to Find It | Common Error | Fix |
|---|---|---|---|
| COGS | Profit & Loss report under Direct Costs / Cost of Sales | Using revenue instead of COGS | Use cost-based figures only |
| Opening inventory | Balance Sheet at the start of the period | Using retail selling value | Use stock value at cost |
| Closing inventory | Balance Sheet at the end of the period | Excluding FBA, 3PL or in-transit goods | Reconcile all stock locations |
| Average inventory | (Opening + closing inventory) ÷ 2 | Using closing inventory only during seasonal spikes | Use average mode for better accuracy |
Useful External References
For accounting definitions and software setup, see Xero's COGS guide, Xero tracked inventory help, QuickBooks stock product setup and A2X ecommerce accounting.
UK Inventory Valuation Rules: Cost vs Net Realisable Value
Inventory turnover depends on accurate inventory valuation. In UK accounting, stock is commonly reviewed at the lower of cost and net realisable value. That means obsolete, damaged or heavily discounted stock may need a write-down if it is no longer expected to recover its cost.
For ecommerce sellers, this matters because old stock can make your balance sheet look stronger than it really is. A SKU might still be recorded at cost, but if it can only be sold after discounts, marketplace fees and fulfilment costs, its recoverable value may be lower.
Accounting Review Point
HMRC guidance recognises stock valuation at the lower of cost and net realisable value. Review stock valuation at cost and net realisable value, then speak to your accountant before writing down material stock balances.
How to Improve Inventory Turnover
Clear Slow-Moving Stock
Create a slow-mover report for SKUs with no sale in 60, 90 and 180 days. Use bundles, email campaigns, marketplace promotions or clearance pricing before storage fees and obsolescence increase.
Buy Based on Sales Velocity
Replace large speculative purchase orders with smaller, more frequent orders based on actual DSI, supplier lead time and minimum order quantities.
Rationalise Your SKU Range
Most stores have a small group of SKUs generating most sales. Remove products that consistently tie up capital without adding margin or strategic value.
Promote High-Margin Stock
Invest PPC and SEO effort into profitable SKUs with enough available stock. Faster turnover is best when it also improves gross profit, not just revenue.
Negotiate Supplier Terms
Shorter lead times, lower MOQs and split shipments reduce the amount of stock you must hold and improve turnover without increasing stockout risk.
Use Inventory Software
Systems like Linnworks, Cin7, Unleashed and inventory modules in accounting software help track stock by SKU, location and sales channel.
90-Day Stock Turnover Improvement Plan
-
Week 1: Build a SKU turnover report
Export COGS, stock value, units sold and stock age by SKU. Group products into fast movers, average movers and slow movers.
-
Week 2: Freeze weak reorders
Stop buying products with weak turnover unless there is a clear seasonal reason, supplier deadline or confirmed sales pipeline.
-
Weeks 3–4: Clear the worst 10%
Discount, bundle or remove the slowest SKUs. For Amazon FBA, compare clearance discount versus storage and removal costs.
-
Month 2: Reforecast best sellers
Set reorder points using DSI, lead time and safety stock. Increase reorder frequency for profitable SKUs with stockout risk.
-
Month 3: Review margin and cash released
Measure improvement in turnover, DSI, gross margin and cash tied up in stock. Repeat monthly as part of management accounts.
Common Inventory Turnover Mistakes
| Mistake | Why It Creates Bad Data | Better Approach |
|---|---|---|
| Using sales revenue instead of COGS | Inflates turnover because revenue includes markup | Use cost-based COGS only |
| Ignoring stock in Amazon FBA or 3PL | Understates inventory and overstates turnover | Include all sellable inventory locations |
| Using only year-end stock | Distorts results for seasonal sellers | Use opening + closing average or monthly averages |
| Combining all SKUs into one ratio | Fast sellers hide dead stock | Calculate by SKU, category and platform |
| Not writing down obsolete stock | Balance sheet may show stock at unrecoverable cost | Review net realisable value with your accountant |
| Only chasing high turnover | Can lead to stockouts and lost marketplace ranking | Balance turnover with availability and margin |
Inventory Turnover vs Sell-Through Rate vs Stock Cover
These three metrics are related but not the same. Inventory turnover is an accounting ratio based on cost. Sell-through rate is a retail units metric. Stock cover shows how many days, weeks or months your current stock can support expected sales.
| Metric | Formula | Best Used For |
|---|---|---|
| Inventory Turnover | COGS ÷ Average Inventory | Accounting efficiency, cash tied up in stock, lender/investor review |
| Days Sales of Inventory | Period Days ÷ Turnover Ratio | Reorder timing, stock age review, cash-flow planning |
| Sell-Through Rate | Units Sold ÷ Units Received × 100 | Retail merchandising, launch performance and buying decisions |
| Stock Cover | Current Stock ÷ Forecast Daily Sales | Stockout prevention and purchase order planning |
Monthly Inventory Turnover Checklist
- Run Profit & Loss and Balance Sheet reports for the same period.
- Confirm COGS includes all product cost and landed cost components.
- Reconcile stock value to warehouse, FBA, 3PL and in-transit inventory reports.
- Calculate turnover and DSI at business, category and SKU level.
- Review SKUs with DSI over 90, 180 and 365 days.
- Check whether slow stock needs discounting, bundling, removal or write-down review.
- Update reorder points for fast sellers based on latest sales velocity.
- Review gross margin after clearance actions to avoid selling below true landed cost.
- Document stock adjustments and write-offs for your accountant.
- Add key stock KPIs to your monthly ecommerce management accounts pack.
Best Practice
Review inventory turnover every month, but make buying decisions using both turnover and margin. A product that turns 10× with poor margin may be less valuable than a product that turns 5× with strong margin and reliable supplier terms.
Automate Your Ecommerce Stock Accounting
Track COGS, stock value, VAT, marketplace fees and payout reconciliation accurately in Xero, QuickBooks or Sage — so your inventory turnover reports are based on reliable numbers.
Inventory Turnover Calculator FAQs
For many ecommerce sellers, 4× to 8× per year is a practical healthy range, but the right benchmark depends on category. Electronics, grocery and consumables usually need faster turnover. Luxury goods, furniture and specialist products can operate with lower turnover if margins and cash flow remain strong.
Inventory turnover is calculated as Cost of Goods Sold divided by average inventory value. Average inventory is normally opening inventory plus closing inventory divided by two. For example, £120,000 COGS divided by £20,000 average inventory equals a 6× stock turnover ratio.
Days Sales of Inventory, also called DSI or days inventory outstanding, estimates how many days stock is held before it is sold. It is calculated as period days divided by inventory turnover ratio. If your turnover is 6× over 365 days, your DSI is about 61 days.
Use COGS, not revenue. Inventory is valued at cost on the balance sheet, so COGS and inventory value are comparable. Revenue includes markup, which would overstate the turnover ratio and make stock efficiency look better than it really is.
Amazon FBA stock should be included in your inventory value because it is still your stock until sold. FBA sellers should calculate turnover by ASIN and review slow-moving inventory regularly because storage fees and aged inventory surcharges can reduce profit on old stock.
Yes. Very high turnover can mean strong demand, but it can also mean understocking. If you frequently sell out, lose Amazon ranking, pause ads or disappoint customers, your turnover is high because stock levels are too low. The goal is profitable turnover with enough availability to meet demand.
Calculate inventory turnover monthly for active ecommerce stock management and quarterly for management accounts. Annual turnover is useful for year-end reporting, but monthly SKU-level review is better for spotting slow movers before they become dead stock.
Stock turnover is a financial ratio based on COGS and inventory value. Sell-through rate is based on units sold compared with units received. Turnover is more useful for accounting and cash-flow analysis, while sell-through is more useful for merchandising and buying decisions.
Yes. Obsolete or slow-moving stock increases average inventory and lowers turnover. It can also overstate your balance sheet if the stock is still recorded at cost but can only be sold below cost. Review old stock for net realisable value with your accountant.
Yes, if COGS and stock values are set up correctly. Use your Profit & Loss report for COGS and your Balance Sheet for inventory value. For ecommerce sellers, integrations such as A2X, inventory apps or SKU-level reports may be needed to produce accurate product-level figures.