Free tool · Inventory
Beginning Inventory Calculator
Work backwards to the opening stock figure when your records are incomplete.
Reconstruct beginning inventory from cost of goods sold, purchases made during the period and your closing inventory. Useful when you are picking up incomplete books, starting a new accounting system, or checking a figure that looks wrong.
- Files never leave your device
- Runs entirely in your browser
- Free, no account needed
How to use Beginning Inventory Calculator
Three steps, and nothing to install.
Enter cost of goods sold
For the period you are reconstructing.
Add ending inventory
The closing figure, ideally from a physical count.
Subtract purchases
Stock bought during the period.
More free tools
Free, private, and no sign-up on any of them.
Finished Goods Inventory Calculator
Value the completed stock you have ready to sell at period end.
Open ToolAverage Inventory Calculator
Work out average inventory value from your opening and closing figures.
Open ToolInventory Turnover Ratio Calculator
Measure how many times you sell and replace your stock in a period.
Open ToolHow do you calculate beginning inventory?
Beginning inventory equals cost of goods sold plus ending inventory, minus purchases made during the period. This reconstructs an opening figure you no longer have on record, which is the usual reason for needing it at year end.
Beginning Inventory Calculator formula
Beginning inventory = Cost of goods sold + Ending inventory - Purchases
Worked example: COGS of 110,000 plus ending inventory of 40,000 less purchases of 120,000 gives a beginning inventory of 30,000.
How this works in your browser
The standard identity states that beginning inventory plus purchases minus cost of goods sold equals ending inventory. Rearranged to solve for the opening balance, that becomes cost of goods sold plus ending inventory minus purchases. Because it is a rearrangement rather than an independent measurement, the answer inherits any error in the three inputs, which is why a negative or implausible result should be read as a signal that one of them is wrong rather than as a figure to record. Computed locally.
Who uses Beginning Inventory Calculator
Taking over incomplete books
Establish an opening figure when records are missing.
Migrating accounting systems
Derive the opening balance for a mid-year switch.
Sense-checking accounts
Verify a stated opening figure against the other three numbers.
Preparing for your accountant
Arrive with a reconstructed figure and the working shown.
Frequently asked questions
What it can and cannot do, and what happens to your files.
How is beginning inventory calculated?
Cost of goods sold plus ending inventory, minus purchases made during the period. It is the standard inventory identity rearranged to solve for the opening figure instead of the closing one.
When would I need to work it out rather than look it up?
When taking over incomplete records, migrating to a new system mid-year, or sense-checking a figure that produces an implausible margin. It is a reconstruction technique, so treat it as a cross-check rather than a substitute for having counted.
Should beginning inventory match last period's closing figure?
Yes, exactly, and any difference needs explaining rather than adjusting away. A mismatch usually means a period adjustment, a write-off or a correction was posted after the previous period was closed.
What if the answer is negative?
Then one of the inputs is wrong, since you cannot start with negative stock. The usual culprits are purchases recorded in the wrong period or a cost of goods sold figure that includes items never actually in stock.
Are my figures stored?
No. The calculation runs in your browser.
Calculate beginning inventory - free.
Files never leave your device. No upload, no account, and free for unlimited use.
Also see: Average Inventory Calculator, Finished Goods Inventory Calculator, Inventory Cost Calculator, Inventory Turnover Ratio Calculator