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DIY Cost Tools

DIY Cost Tools

Inventory Turnover Calculator

Estimate how often average inventory turns over during a stated reporting period. Use cost of sales rather than selling-price revenue so numerator and inventory use a comparable cost basis. Enter beginning and ending balances for that same period. The days result converts the period turnover into an approximate duration; a quarterly calculation should use quarter days rather than 365. Check seasonal businesses with more frequent inventory observations if possible.

Enter every field, including explicit zeros when permitted. Decimal and scientific notation are accepted; commas, fractions and blanks are rejected. Each input must be finite and no larger than 1 billion in absolute value. Observe the units and positive-value requirements below.

Average inventory (currency)30000
Turnover for period (times)8
Estimated inventory days45.625

How to use this calculator

  1. Match your inputs to the stated financial model and field labels.
  2. Convert your quantities to the units printed next to each field.
  3. Select Calculate, or press Enter, and read the labeled results.

Formula and method

Average inventory = (beginning + ending)/2; turnover = cost of sales/average inventory; inventory days = period days/turnover.

The calculation runs in your browser. After changing an input, select Calculate again. Invalid inputs or undefined mathematical conditions hide the previous result so it cannot be mistaken for an answer to the new values.

Worked example

Cost of sales of 240,000 and beginning/ending inventories of 20,000/40,000 give average inventory of 30,000. Turnover is 8; for a 365-day period, inventory days are 45.625.

Limitations and interpretation

Use one currency and consistent reporting dates. This is an educational calculation, not investment, lending, tax or accounting advice. A ratio alone cannot establish solvency, creditworthiness or fair value; review the underlying statements and consult a qualified professional for consequential decisions. A two-point average can miss seasonal inventory peaks. The tool does not annualize automatically or assess stockouts, obsolescence or industry norms. Positive cost of sales and average inventory are required.

The numerical conditions stated above are enforced by the calculation. Read each error message before changing a value. Results use floating-point arithmetic and are shown to approximately 10 significant digits. Monetary estimates and financial statements generally do not justify treating all of those digits as precise. Enter all monetary inputs in one currency; no exchange rates are fetched.

Frequently asked questions

Do I enter sales revenue or cost of sales?

Use cost of sales for this version. Revenue-based turnover is a different convention and can change the comparison.

Why do currency and reporting dates matter?

Use the same currency and compatible reporting dates or periods for every input. The calculator does not fetch market data, translate currencies or classify your accounts. Example amounts are hypothetical.

Does this result recommend a financial decision?

No. The result evaluates the stated formula using your inputs. It does not recommend borrowing, investing or changing an accounting policy. Consider the wider situation and obtain professional advice when appropriate.

Review notes and reference

Reviewed October 3, 2026. The default worked example and an additional boundary or scaling check were tested against expected values. Validation checks included blanks, nonnumeric text and inputs outside the supported range. Financial-method reference provides background for the financial concepts used here. The text and worked example on this page are original.

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