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Inventory accuracy and cycle counting

Find out how far the system balance can be trusted — by item and by value — and build a cycle count plan your team can keep up with every day.

Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.

CheckRevised 11/05/2026
Part 1 — count accuracy
Items counted
See what was read

Prefer the class from the ABC analysis of the whole item master. If left blank, the page calculates it, but only from the items counted (an approximation); without the usage column, it uses stock value (balance × cost).

Tolerance (± % of system balance)
Part 2 — cycle count plan
Items in the item master
Counting frequency
Team capacity

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—Accuracy by item
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Accuracy by class

Key: class (tolerance); correct / items = within tolerance / counted in the class; accuracy by item = correct ÷ items; system value = balance × cost; gross difference = sum of money differences ignoring sign; accuracy by value = 1 − gross ÷ system value; net adjustment = overages − shortages.

Accuracy by item vs by value, by class

Two bars per class and the target.

Tap the chart to see the values.

How to read: for each class, the left bar is the share of correct items and the right bar the share of correct value. The dashed line is the target. Value bars much higher than item bars show errors concentrated in cheap items; the opposite means errors in expensive items — the most serious case.

Pareto of the largest value differences

The 10 items with the largest money difference (ignoring sign), with their share of the total.

Tap the chart to see the values.

How to read: each bar is one item, from the largest money error to the smallest; red = shortage (physical below system), blue = overage. The number beside it is the difference and its share of the total gross error. The first items usually explain almost all of the value error: investigate their cause before adjusting.

Items counted

Sorted by value difference. Difference = physical − system (negative = shortage). Download as .xlsx at the end of the page.

Cycle count plan

Summary calendar: how many items of each class to count per year, month, week and day, and every how many working days the same item is counted again.

Items vs counting effort by class

Share of master-file items and share of the year’s counts in each class.

Tap the chart to see the values.

How to read: for each class, the first bar is its share of master-file items and the second its share of the year’s counts. In a good plan, A items, few and expensive, get a much larger share of counts than of items; C items, many and cheap, a smaller one.

Next step

Take this page’s results to another calculator with the fields already filled in.

Take accuracy to the logistics KPI dashboard →Full ABC analysis of the items →Pareto of the differences →Safety stock and reorder point →Inventory turnover and carrying cost →

The calculation report gathers this page's inputs, results, equations, assumptions and references, with fields for project, engineer and revision. The full report also includes the charts and interpretations, in color. In the print dialog, choose Save as PDF.

Method, assumptions and references

Equations used

Item correct if |physical − system| ≤ class tolerance × system (with system = 0, only if physical = 0)
Accuracy by item = correct items ÷ items counted; accuracy by value = 1 − Σ|physical − system|·cost ÷ Σ system·cost
Gross difference = Σ|physical − system|·cost; net adjustment = Σ(physical − system)·cost = overages − shortages
Calculated class: items ranked by annual value (cost × usage; without usage, balance × cost); A up to the A limit of the cumulative share, B up to the B limit, the rest C
Counts per year = Σ items in class × times per year; per day = counts per year ÷ working days; interval = working days ÷ times per year
Counters = items per day × (1 + recounts) × minutes per item ÷ (hours per counter × 60)

Assumptions and limits

  • Tolerance is relative to the system balance and applies per item; some companies use a value tolerance (e.g. ± $10) for C items — in that case, convert it to a percentage of the balance.
  • Sample accuracy represents the whole stock only if the counted items were chosen at random (or it is a full count). Items counted because an error was suspected give a worse accuracy than the real one.
  • The plan assumes counts spread evenly over the working days and the same average time per item in every class.

Standards and technical documents

  • ASCM (APICS) Dictionary, 17th ed.: inventory accuracy, cycle counting, tolerance
  • Heizer, J.; Render, B.; Munson, C. Operations Management, 13th ed. Pearson, 2020, cap. 12 (Inventory management: record accuracy and cycle counting)
  • Brooks, R. B.; Wilson, L. W. Inventory Record Accuracy: Unleashing the Power of Cycle Counting, 2nd ed. Wiley, 2007
  • Arnold, J. R. T.; Chapman, S. N.; Clive, L. M. Introduction to Materials Management, 8th ed. Pearson, 2017 (inventory record accuracy, ABC)

U.S. regulations

  • ASC 330 (Inventory): measurement of inventory and write-downs for shrinkage
  • IRC §471 and Treas. Reg. 1.471-2: inventory records and shrinkage estimates for tax purposes
  • Sarbanes-Oxley Act §404 (public companies): internal control over inventory records

Frequently asked questions

How do I calculate inventory accuracy?

Count a sample of items, compare with the system balance and divide the items within tolerance by the total counted. In the example, 16 of 20 items within tolerance = 80%. Also calculate accuracy by value, which weighs each error by cost.

What is a count tolerance?

It is the difference accepted between physical and system for the item to still count as right. Expensive A items usually have zero tolerance; cheap C items counted by weight, up to 5%. Do not use tolerance to hide errors: it only acknowledges the limit of measurement.

Why is accuracy by item different from accuracy by value?

Because by item counts every code the same, and by value weighs each error by money. Many errors on bolts pull down item accuracy but barely move value accuracy; a single missing motor does the opposite.

What are net and gross adjustments?

Gross adds up the differences ignoring sign and shows the real size of the error. Net is overages minus shortages and is what goes to accounting. A net close to zero can hide a large gross, with some items over and others short.

How often should each class be counted?

A common scheme is A monthly, B quarterly and C once or twice a year. Adjust from history: items with many errors or heavy movement deserve more counts, whatever their class.

How many items should be counted per day?

Add up items × frequency for each class and divide by working days. With 320 A items × 12, 640 B × 4 and 2,240 C × 1 over 250 days, that is about 35 items a day — at 6 minutes each, under 4 hours for one counter.

Does cycle counting replace the annual physical inventory?

In many companies, yes, as long as the program is documented, accuracy is measured and the auditors accept the method. Check with accounting and the auditors before dropping the full physical count.

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