Cost of goods sold is the cost of the stock your shop sold during a period.
Key takeaways
- Gather the beginning balance, unit costs, and purchase invoices.
- Use the same cutoff for purchases and the physical count.
- Value counted stock using your cost method, then subtract it from goods available for sale.
- Post the adjustment before preparing the period's statements.
It is not the shelf price, and it is not simply what you paid for stock this month. At period end it is worked out from goods available for sale and ending inventory, valued using your cost method. Get those inputs right, and the subtraction that ties them together is the easy part.
Most of the trouble with this figure comes from the inputs rather than the arithmetic. A purchase invoice filed in the wrong month, a count sheet with no unit costs, or a cost method changed partway through the year will each move the result, and none of them announces itself. The steps below follow the order you would work through them at close, so each figure is ready before the next one needs it.
Your staff usually does the physical count. The owner or manager usually settles the cost method and posts the result, and both should agree on the cutoff date before the count starts. The steps assume you count stock at the end of the period, rather than tracking cost against every sale as it happens. That is the periodic method, and it is the setting in which these three figures are easiest to see.
Shops that count only once a year, or on a rotating schedule, face the same three figures at each close. The arithmetic does not change. What changes is how much of the count can be done before the period ends and how much has to wait until the books are closed.
The figure matters beyond the close. It feeds gross margin, which shows how much each sale keeps after its stock cost, and it is a common input to pricing and buying decisions. This post is written for shop owners, managers, and the staff who count at period end. If you only need the final number, step 4 is where it appears, but the first three steps decide whether that number means anything.
1. Start with the beginning balance and its unit cost
Your beginning balance is the cost of the stock on hand when the period opened. Take it from the books, and take it before any period-end adjustment is posted. The adjustment is the thing this process produces, so starting from an adjusted figure would hide the very change you are trying to measure. A worked example from OpenStax begins with beginning merchandise inventory of $3,150 before adjustment, and the figures that follow in this post build from that opening point.
If your books live in a spreadsheet rather than accounting software, the opening figure should be the balance carried forward from the last close. It should not be a number typed in partway through the month, because every later step inherits whatever sits at the top.
Unit cost matters as much as the total. A single average can make the opening balance look right while the lots underneath it are wrong. Two lots of the same item often arrive at different prices in one period, and only the invoices show that. The invoice shows what you paid, and only that figure belongs in this calculation.
OpenStax assumes a beginning inventory cost of $21 for each unit for simplicity of demonstration. Your shop may have different costs across a product line, so treat that $21 as a teaching shortcut rather than a pattern to copy. Once you have the real unit costs, you can see which lines carry the most dollars and which ones need the most attention before the count begins. For a closer look at valuation, see how to value a stock count.
Before the count starts, give the count team the beginning balance and each item's unit cost. A team that counts with costs printed beside the quantities does not have to hunt for prices after the fact, and the sheet becomes the one place where quantity and cost meet. Blank cost columns push the valuation work to the end of the close, which is exactly when the pressure to finish is highest.
The beginning balance also sets up the next period. If the books changed systems during the year, carry the opening figure across from the old records in one piece, rather than rebuilding it from memory.
2. Add purchases to get goods available for sale
Goods available for sale is the beginning balance plus everything that came into stock during the period. In most shops that means purchases from suppliers, plus any other additions your books record to inventory. Think of it as one pool of cost. Everything that left the shop and everything still on the shelves was drawn from that pool, so the two figures you calculate later can only be as accurate as this total.
In the example, the total of goods available for sale is $16,155. That number is the ceiling for the whole split. Every dollar in it either stayed in the stockroom at period end or left as cost of goods sold, and nothing else is available to divide between the two.
Build the total from source documents, not from memory or a running estimate. Pull the purchase invoices dated in the period, list each one with its date, supplier, and amount, and add them to the beginning balance. One list in one place makes a missing invoice easy to spot, and it gives anyone reading the close a concrete trail to follow. Returns to suppliers reduce what you bought, so they come off the total as well.
Purchases from several suppliers are easy to undercount when each supplier sends statements on its own schedule. Gather the invoices for the whole period from every supplier account before anyone totals anything, including the small orders that were paid on the spot and never went through the main ordering process.
Set the cutoff before you start. The cutoff is the date after which deliveries belong to the next period, and the same date should govern both the purchase list and the count. If a delivery reaches the count but is missing from the purchase list, the ending inventory picks up stock the pool never included, and the cost of goods sold comes out low. If a delivery that arrived after the cutoff is added to the pool anyway, the cost of goods sold comes out high. A missed invoice makes the figure look like a better margin than the shop actually earned, which is why this total deserves as much care as the count.
Items used up in running the shop, such as cleaning supplies or shopping bags, are not stock held for resale, so they stay out of this pool. Including them would load the cost of goods sold with costs that never went to a customer.
3. Count and value the ending inventory
Count every unit on hand at the cutoff, then assign each unit a cost under your cost method. The count gives you quantity, and the cost method gives you dollars. These are two separate jobs, and most valuation problems start when they get mixed together, such as when a bin is priced at whatever figure is easiest to find that day.
It helps to count in a fixed order, the same route every time, so that no item is counted twice or skipped. Mark each shelf or bin as it is finished. Working in pairs, with one person calling quantities and the other writing them down, cuts down on misread numbers. Items sold by weight or length need to be counted in the same unit the costs use, so a case and a single unit are never mixed on one line. Damaged or unsaleable units should be noted separately on the sheet, so the total can be explained rather than buried. Use the physical inventory reconciliation steps to review the count before posting changes.
Ending inventory is the cost of goods still on hand at period end. It is not units multiplied by the current selling price. It is the cost that the method assigns to the units that remain.
The method decides which costs stay on the shelf. In the example, 300 of the 585 units available for the period were sold. Under FIFO, the earliest acquisitions are considered sold first, so the units that remain are the ones that were purchased last. Specific identification works differently. It follows the cost of each individual unit, which suits stock that is small in number and distinct from one item to the next.
Choosing among methods is partly a question about how your stock moves. Goods that turn over within a few weeks and arrive at steady prices tend to produce little difference between methods. Goods that sit for months while supplier prices change can produce a large one, which is why the same count can look very different depending on the method applied to it.
Before you change methods, talk with an accountant. A change in method changes the ending inventory and the cost of goods sold even when the count is identical, and it changes how this period lines up with the ones before it.
Keep the count sheets, the purchase invoices, and a short note of the method used in one file for the period. When someone asks later where a dollar value came from, the answer should be in that file.
Here are the example's figures side by side, with what each one stands for:
| Figure | Amount in the example | What it stands for |
|---|---|---|
| Beginning merchandise inventory | $3,150 before adjustment | Balance the period opens with |
| Goods available for sale | $16,155 | Beginning balance plus additions for the period |
| Ending inventory | $8,955 | Cost of goods still on hand at period end |
| Cost of goods sold | $7,200 | Goods available minus ending inventory |
| Gross margin, specific identification | $7,260 | Result under the specific identification periodic cost allocation |
4. Subtract ending inventory to get cost of goods sold
Subtract ending inventory from goods available for sale, and the difference is cost of goods sold for the period. The arithmetic is one line, which is why errors in this step usually trace back to the total or to the count rather than to the subtraction itself. In the example, subtracting this ending inventory from the $16,155 total of goods available for sale leaves $7,200 in cost of goods sold this period.
Think of the period as a bridge between two points: what you started with plus what came in, and what you still hold at the end. Cost of goods sold is the part that crosses over to customers. Seen this way, the figure answers one question, which is how much of the stock pool left the shop as sales.
Put the three figures side by side, in the order they were calculated: goods available, ending inventory, and the difference. Anyone reading them can then follow the subtraction without asking where a number came from. Whoever reads your books next will look for these three figures first, so they should be complete before anyone outside the shop sees them.
The sales total does not enter this calculation at all. Gross margin is what remains when this figure comes off sales, so it moves whenever the cost method moves. Two periods with the same sales can therefore show different margins if the method changed between them, and that difference belongs in the explanation for the period rather than in a surprise later.
Carry the cost of goods sold figure to the income statement.
Illustrative example: a smaller stock pool
Suppose goods available for sale cost $20 and counted ending inventory costs $10. Subtract $10 from $20: cost of goods sold is $10. These illustrative amounts show the subtraction after the stock has been counted and valued.
5. Post the adjustment that brings the books to the count
The count sets the balance the books must reach. That entry is the tool that moves the book balance to the counted figure. Post it before the period's statements are prepared, so the balance sheet and the cost of goods sold figure come from the same count.
Under the periodic method described here, the merchandise inventory book balance is the beginning balance carried forward before adjustment. The count is the independent figure the entry is measured against, which is why the amount of the entry comes from the counted figure and not from an estimate. On the balance sheet, merchandise inventory is the asset this entry sets. Once it matches the count, the balance sheet and the income statement describe the same stock from two sides, which is the point of counting at all.
Post the entry in the period the count belongs to, so it does not land in the next period by accident.
Once the entry is posted, the period-end balance becomes the next period's beginning balance. Start the next count from the same unit cost sheet you used this time, and update only the lines whose costs changed.
Your next step today
Gather the opening balance, purchase invoices, and count sheets in one file, then check that they use the same cutoff before calculating the total.
Questions about cost of goods sold
What should I check if the result looks wrong?
Check the opening balance, purchase cutoff, counted quantities, and unit costs first. Follow the steps above to trace each input back to its record.
Where should I keep the calculation?
Keep it in the period's file with the count sheets, purchase invoices, and cost-method note. That keeps the result beside the records needed to explain it.