Beginning Inventory Calculator
Opening stock reconstructed from the period's figures.
Optional — enter a counted value to see shrinkage.
Beginning inventory
$30,000
COGS + ending − purchases
How the Beginning Inventory Calculator works
The opening figure is normally just the previous period's close. When records are incomplete — a first set of accounts, a system migration, a missed count — it can be reconstructed by running the inventory equation backwards.
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Frequently asked questions
How is beginning inventory calculated?
Cost of goods sold + ending inventory − purchases. Ending at £35,000 with £80,000 of purchases and £75,000 of COGS implies £30,000 of opening stock.
When would I need to calculate it?
Reconstructing incomplete records, migrating between systems, preparing a first set of accounts, or checking whether a reported opening figure is consistent with the rest of the period.
Does beginning inventory affect profit?
Yes, through COGS. Cost of goods sold is opening inventory plus purchases minus closing inventory, so an overstated opening figure inflates COGS and understates profit for the period.
What if the calculated figure looks wrong?
One of the other three numbers is wrong, or there is unrecorded shrinkage. The equation only balances when all the inputs are accurate, which makes a surprising result a useful audit signal rather than an answer to accept.