What Is a Good Inventory Accuracy Rate for an Ecommerce Warehouse? UK Benchmarks and How to Measure It

A good inventory accuracy rate for an ecommerce warehouse is 99.5% or higher measured by location, the best-in-class threshold in the 2025 WERC DC Measures report. By units, the median warehouse in an earlier WERC study ran above 99.6%. Below 98% signals a process problem. The number only means something once you know how it was counted.

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Two warehouses can both report "99% accuracy" while one is far more reliable, because they count different things. Below are the benchmarks, the formulas, a worked example and the contract wording that makes a 3PL's number comparable.

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Inventory record accuracy is the share of counted stock where the quantity and location in the warehouse system match what is physically on the shelf.

Benchmarks by measurement method

The right benchmark depends on the method: 99.5% or more is best in class by location, above 99.6% is typical by units, and pick accuracy is a separate measure. The main published benchmark comes from the Warehousing Education and Research Council's (WERC) annual DC Measures report, based on a US survey of distribution professionals. We could not find a UK body that publishes an equivalent figure, so WERC's definitions are the practical reference for UK brands too.

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• Location accuracy. How it's counted: Locations with zero variance ÷ locations counted. Typical benchmark: Best in class 99.5% or higher; below 98% flagged as needing improvement. Source: WERC 2025 DC Measures, via Yale infographic; RF-SMART summary of WERC.
• Unit or value accuracy (absolute variance). How it's counted: 1 minus (sum of every over and under, ignoring sign ÷ units or £ on record). Typical benchmark: Median above 99.6%, best in class 99.98% (2008 WERC study). Source: Kate Vitasek, Supply Chain Digest.
• Net unit or value accuracy. How it's counted: Counted total ÷ book total, with overs and unders allowed to cancel. Typical benchmark: No credible benchmark: overs offset unders, so the figure flatters. Source: Supply Chain Digest on measurement methods.
• SKU record accuracy (exact match per record). How it's counted: Records with exactly the right quantity ÷ records checked. Typical benchmark: 65% of nearly 370,000 store records were wrong in one retail study. Source: DeHoratius and Raman, Management Science.
• Order picking accuracy (not inventory accuracy). How it's counted: Orders picked without error ÷ orders picked. Typical benchmark: Best in class 99.68% or higher. Source: WERC 2025 DC Measures, via Yale infographic.

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Two points matter most. First, location accuracy is the hardest test, because a unit in the wrong bin counts as a failure even if the warehouse total is right. Second, pick accuracy and inventory accuracy are different KPIs. Fulfil with Synergy's AutoStore pick accuracy of 99.99% measures how often the right item reaches the right order; it is not a stock record figure, and you should never let a provider present one as the other. Our guide on how to read a 3PL's accuracy SLAs covers order accuracy in more depth.

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The two are linked, though. When a picker takes SKU B instead of SKU A, the order goes wrong and two stock records go wrong with it: A shows one fewer than is on the shelf and B shows one more. That is why automated picking matters for stock accuracy, and why Fulfil with Synergy runs its RedPrairie Dispatcher WMS and AutoStore set-up in Northampton as one connected system.

How to calculate it

Pick a method, count a defined sample, compare it with the system at the same moment and use one of the calculation methods below. Freeze movements in the counted locations while you count, or the system figure will change under you.

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Location accuracy: Divide the number of counted locations with no variance by the total number of locations counted, then multiply by 100.

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Absolute unit accuracy: For each stock record in your sample, calculate the difference between the physical count and the system quantity, treating both shortages and surpluses as positive amounts. Add those differences together and divide the result by the total system units in the same sample. Subtract that result from 1, then multiply by 100.

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Net unit accuracy: Calculate the difference between the total physical count and the total system quantity for the same sample, treating the difference as a positive amount. Divide it by the total system units, subtract that result from 1, then multiply by 100.

Avoid the simple "counted ÷ recorded" ratio: it exceeds 100% when you find extra stock and lets a shortage in one bin cancel a surplus in another.

Worked example

A warehouse counts 200 locations. The system says those locations hold 10,000 units. 194 locations match exactly. Six do not:

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• A (SKU 101). System: 120. Counted: 100. Variance: −20.
• B (SKU 101). System: 0. Counted: 20. Variance: +20.
• C. System: 50. Counted: 48. Variance: −2.
• D. System: 30. Counted: 31. Variance: +1.
• E. System: 200. Counted: 190. Variance: −10.
• F. System: 40. Counted: 43. Variance: +3.

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Locations A and B are the classic put-away error: 20 units of SKU 101 went into the wrong bin. Now apply the formulas:

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• Net unit accuracy: total variance is −8 units. 1 − (8 ÷ 10,000) = 99.92%
• Absolute unit accuracy: total absolute variance is 56 units. 1 − (56 ÷ 10,000) = 99.44%
• Location accuracy: 194 ÷ 200 = 97.0%

Three ways the same warehouse can report three different numbers

The same count above produces 99.92%, 99.44% or 97.0%, depending on the formula, and all three are honest calculations. Which one you are shown changes the story completely.

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Net units hide misplaced stock. At 99.92%, this warehouse looks excellent, yet SKU 101 could show as out of stock while 20 units sit in the wrong bin.

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Absolute units count every mistake once. At 99.44%, the warehouse sits just below the 2008 WERC median. It is a fairer measure of how much stock is wrong, but it still does not tell you whether stock is findable.

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Location accuracy tests whether you can sell from the record. At 97.0%, this warehouse falls below the 98% line that marks a process problem. For an ecommerce brand selling across Shopify, Amazon and retail from one stock pool, this is the number that predicts overselling and cancelled orders.

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There is a fourth lever: tolerance. As Supply Chain Digest's review of measurement methods sets out, some operators allow a small variance before a location counts as wrong, and some apply tighter tolerances to high-value lines. If this warehouse allowed ±2 units, locations C and D would pass and location accuracy would rise to 98.0%. That may suit bulk pallets of low-cost items; for a £45 serum, two units is a real loss.

What to put in your 3PL contract

A useful 3PL inventory accuracy SLA names the method, the tolerance, the sample and the reporting, not just a percentage. Without those four, a "99%" target can be met while your stock records are unusable.

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Ask for these terms in writing:

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1. Method. Location accuracy as the headline KPI, with absolute unit accuracy reported alongside. Rule out net figures as the contractual measure.
2. Target. 99.5% or higher by location is a reasonable target for a WMS-led, barcode-scanned operation, reviewed after onboarding once the starting position is known.
3. Tolerance. Zero tolerance for high-value or small-unit SKUs; any tolerance for bulk lines stated in units, not percentages.
4. Sample and frequency. Which locations are counted, how often and who chooses them (whether stock is checked by rolling cycle counts or an annual stocktake is decided here).
5. Exclusions. Whether stock in goods-in, quarantine or returns processing is in or out of the count.
6. Variance handling. How adjustments are investigated, approved and reported, and how unexplained losses beyond tolerance are treated commercially.
7. Reporting. Monthly accuracy by method, plus a log of every stock adjustment with reason codes, visible to you without having to ask.

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Review the result alongside the fulfilment metrics worth reviewing every month, so accuracy is read next to adjustments and returns rather than on its own.

How Fulfil with Synergy tracks and reports stock accuracy

Fulfil with Synergy measures stock at the level a brand sells it: every unit, SKU, batch and location is tracked live in RedPrairie Dispatcher WMS, and every movement has an audit trail clients can see. Fulfil with Synergy is a founder-led UK 3PL and growth partner for ambitious, fast-growing consumer brands, operating a technology-led fulfilment centre in Northampton for health, wellness, beauty, supplement and lifestyle brands across D2C, marketplace, retail and wholesale channels.

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In practice, that means:

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• Accuracy starts at goods-in. Cubiscan captures weight, dimensions and imagery for each SKU on arrival, and stock is scanned, located and reconciled against the advance shipping notice. Discrepancies are flagged in real time, photographed, logged and resolved jointly with the brand.
• Every movement is traceable. The WMS keeps a full stock movement audit trail that is time-stamped, user-tagged and categorised, so a variance can be traced to the exact put-away, pick or adjustment that caused it. Read more on how RedPrairie Dispatcher tracks every unit by batch and location.
• Batch and date control is automatic. FEFO and FIFO rules run in the WMS, which matters for supplements and skincare where the wrong batch is as much an error as the wrong quantity.
• Picking protects the record. The 57,000-tote AutoStore grid, with pick-to-light at the ports, delivers 99.99% pick accuracy. Fewer mis-picks means fewer of the paired stock errors described above.
• You see what we see. The 24/7 client portal shows live inventory, inbound status, orders and returns, with custom reports and data available by API, SFTP or flat file.

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Each brand has a named Client Manager and a Client Support Specialist on the floor, with weekly operational reviews and monthly business reviews covering stock and adjustments. For brands moving from another provider, onboarding ends with a formal stock reconciliation report, so the accuracy baseline is agreed before trading starts rather than argued about later.

FAQ

Is 95% inventory accuracy good?

No, 95% is too low for an ecommerce warehouse selling across several channels. By location, it means one in every 20 bins holds the wrong quantity or the wrong product, and WERC flags anything below 98% as needing improvement. Some blogs quote 95% as a target without a source; the published benchmarks set the bar much higher. Aim for 99.5% or more by location. If a provider is reporting 95% on a net unit basis, the location figure is likely to be lower still.

Can inventory accuracy be more than 100%?

Not if it is calculated properly. A figure above 100% almost always comes from the "counted ÷ recorded" formula when the count finds more stock than the system expects. Surplus stock is still an error: it usually means a receipt was missed or a unit was put in the wrong place, and somewhere else is probably short. Use absolute variance, where overs and unders both reduce the score, so your accuracy rate tops out at 100% and every discrepancy counts against it. When a supplier report shows figures above 100%, ask for the location-level count behind it before accepting it.

What is the difference between inventory accuracy and order accuracy?

Inventory accuracy measures whether the stock records match the shelves; order accuracy measures whether customers receive exactly what they ordered. A warehouse can hit 99.9% order accuracy while location accuracy is poor, because pickers find the stock anyway. The reverse also happens. Ask for both, measured separately, and check that a headline "99% accuracy" claim says which one it means and over what period. Fulfil with Synergy's 99.99% figure is AutoStore pick accuracy, an order measure, and is reported separately from stock record accuracy for exactly this reason.

Why is my inventory accuracy dropping across channels?

Stock accuracy usually drops across channels because each sales channel holds its own view of stock and updates it at different speeds, while the warehouse record drifts through put-away, returns and manual adjustments. The fix starts with one stock pool in one WMS feeding every channel, then measuring location accuracy monthly so drift shows up before customers see cancelled orders. We cover the five most common causes of channel stock drift separately, including separate stock pools, manual updates and returns handling.

What should real-time inventory tracking at a 3PL actually show me?

Real-time inventory tracking should show live stock by SKU, batch and location, inbound deliveries not yet put away, stock allocated to open orders, returns in processing and a log of every adjustment with a reason. If a provider can only send a daily spreadsheet, it is not real time, and you will be selling against yesterday's stock during your busiest hours. Fulfil with Synergy's portal shows live inventory, ASN status, orders and returns, with data by API. See what a fulfilment client portal should show you.

A good inventory accuracy rate is 99.5% or higher, measured by location, with absolute unit accuracy above 99.6% reported alongside and every adjustment visible to you. Anything quoted without a method, tolerance and sample cannot be compared with anything else.

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Fulfil with Synergy runs that measurement on RedPrairie Dispatcher WMS with a full audit trail, AutoStore picking and a live portal, so brands can check their stock rather than take it on trust. If you want to see how your current provider's figure would look under these definitions, talk to the Fulfil with Synergy team about measuring your stock accuracy.

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