Inventory Turnover Calculator: Turns, Days and GMROI

Inventory Turnover Calculator

Calculate inventory turnover, days inventory on hand, gross margin return on inventory and the average inventory needed for a target turnover rate. Keep cost of goods sold and inventory on the same accounting-cost basis.


Enter annual turns when the reporting period is one year. For another period, use a turnover target for that same period.

Your inventory metrics

Average inventory—
Inventory turnover—
Days inventory on hand—
Gross profit—
GMROI—
COGS as % of sales—

Turnover is for the entered reporting period. Compare it only with targets or businesses using compatible periods, inventory-cost methods and product mixes.

Inventory turnover formulas

The SEC describes inventory turnover as cost of sales divided by average inventory. When only beginning and ending balances are available, this calculator uses their simple average.

Average inventory = (beginning inventory + ending inventory) ÷ 2
Inventory turnover = cost of goods sold ÷ average inventory
Days inventory on hand = days in period ÷ inventory turnover
GMROI = (net sales − cost of goods sold) ÷ average inventory

GMROI is shown only when net sales are entered. It expresses gross profit per currency unit of average inventory; it is not net profit and excludes operating expenses, financing, taxes, shrinkage and markdowns not already reflected in the inputs.

Checked example

Suppose beginning inventory is $80,000, ending inventory is $100,000, annual cost of goods sold is $540,000 and annual net sales are $900,000. Average inventory is $90,000, inventory turnover is 6.00 times, and days inventory on hand are 60.83 days. Gross profit is $360,000 and GMROI is 4.00.

With a target of 8.00 turns for the same annual period, target average inventory is $67,500 and target days on hand are 45.63. Holding cost, service levels and stockout risk are not estimated, so a lower inventory target is not automatically better.

Input consistency and limits

  • Use inventory and cost of goods sold on the same cost basis and for the same reporting period.
  • A two-point average can misrepresent seasonal or rapidly changing inventory. If available, use a monthly, weekly or daily average and select “Average inventory directly.”
  • Do not mix retail selling-price inventory with cost-basis COGS unless both have been converted consistently.
  • Industry comparisons require compatible accounting methods, seasonality and product mixes. There is no universal “good” turnover rate.
  • This educational estimate does not replace accounting records, physical counts, tax advice or inventory-planning software.

Official references: SEC Beginner’s Guide to Financial Statements, IRS Publication 538 for inventory valuation methods, and the U.S. Census Bureau retail definitions for its separate end-of-month inventory-to-sales measure.

Related calculators

Use the Margin Calculator for margin and markup, the Break-Even Calculator for the sales volume needed to cover costs, the Customer Lifetime Value Calculator for customer economics, or the Business Valuation Calculator for scenario-based company value.