Business health calculator
Inventory Turnover & Stock Days Calculator
Turn cost of goods sold and your inventory into inventory turnover and stock days. Your entered values stay out of analytics.
Formula and assumptions
Turnover = cost of goods sold ÷ average inventory. Stock days = average inventory ÷ cost of goods sold × days in the period.
- Average inventory is the average of opening and closing stock, or the figure you enter.
- The period is 365 days for a year. Change it if you use a different period, and use sales or purchases for the same period.
- A high or low turnover means different things for different kinds of business.
- Days are shown to 2 decimal places (half up).
Formula version 1.0, last reviewed 1 October 2026.
Frequently asked questions
What is stock days?
The average number of days your stock sits before it is sold, also called days inventory outstanding.
Which inventory figure should I use?
The average of opening and closing stock for the period, or an average you already work out from monthly figures.
Is a higher turnover better?
It depends on the trade. Fast-moving goods turn over often; machinery does not. Compare with your own earlier periods.