Cost of Goods Sold Calculator for Resellers
Enter your opening inventory, what you bought and what is left unsold to get the cost of goods sold for the year.
Free · runs in your browser · nothing is uploaded
How to use the cost of goods sold calculator
- Enter what your stock cost on 1 January in “Inventory at the start of the year”.
- Enter everything you bought to resell this year, at cost, in “Purchases during the year”.
- If you include other costs in cost of goods, such as costs of getting items ready to sell, add them in “Other cost of goods (optional)”. Leave it empty if not.
- Enter what the unsold stock cost you on 31 December in “Inventory at the end of the year”.
- If you want the gross profit line, enter your total sales in “Sales for the year (optional)”.
- Read the table: “Goods available for sale (opening + purchases + other)” and “Less closing inventory”. Below it, “Cost of goods sold” is the result, followed by the gross profit when you entered sales.
The page starts empty and shows no result until you enter purchases or opening inventory. If you started the year with no stock, leave the opening inventory empty. Use cost, not the price you hope to sell for, for every stock figure. A warning appears if the result is negative. The page has no link, CSV or ledger button, so note the result down, or keep the underlying purchases in the reselling spreadsheet.
What is the formula for cost of goods sold?
Cost of goods sold is the opening inventory plus purchases plus any other cost of goods, minus the closing inventory. The sum of the first three is goods available for sale. The IRS Schedule C instructions use the same logic in Part III. The page does the arithmetic and does not decide what you may include.
| Line | Amount |
|---|---|
| Inventory at the start of the year | $1,200.00 |
| Purchases during the year | $5,800.00 |
| Goods available for sale | $7,000.00 |
| Less inventory at the end of the year | $900.00 |
| Cost of goods sold | $6,100.00 |
With $10,000.00 of sales, the gross profit line reads $3,900.00 (39.0% of sales).
How does inventory change cost of goods sold?
Closing stock lowers the result, because goods you have not sold are not a cost of this year. Opening stock raises it, because it was available to sell. In the example, stock fell from $1,200 to $900. You sold the $5,800 you bought plus $300 of older stock, so cost of goods sold is $6,100.
If instead your stock grew from $1,200 to $2,000, cost of goods sold would be $1,200 + $5,800 − $2,000 = $5,000, less than your purchases.
Do I have to count inventory at all?
The IRS Schedule C instructions say that inventories at the beginning and end of the year generally have to be taken into account when buying or selling merchandise is an income-producing factor. They also describe simpler options for small business taxpayers, who must still use a method that clearly reflects income. Which rule applies to you is for the instructions, IRS Publication 538 or a tax adviser.
Can cost of goods sold be negative?
Not in a sensible set of figures. A negative result means the closing inventory is larger than the stock you had available, so one number is probably mistyped or the closing stock is valued above cost. The page shows a warning in that case.
How this tool works and where the numbers come from
Cost of goods sold is the opening inventory plus purchases (and any other costs you include) minus the closing inventory, which is the arithmetic behind Part III of Schedule C. The IRS instructions say inventories at the beginning and end of the year generally have to be taken into account when merchandise is an income-producing factor, and small business taxpayers have simpler options; the instructions and Publication 538 decide which applies to you.
Sources
- IRS: Instructions for Schedule C (Part III, cost of goods sold) (updated 30-Apr-2026) · checked
- IRS: What to do with Form 1099-K (Page last reviewed or updated 27-Jul-2026) · checked
Frequently asked questions
What is cost of goods sold?
It is the cost of the stock you sold in a period: what you paid for it, not what you sold it for. For a reseller, it is opening stock plus purchases less what is still unsold.
What counts as cost of goods?
The page adds the purchase cost you enter, plus anything in the optional “Other cost of goods” line. Which costs belong there is a question for the Schedule C instructions and Publication 538, not for this page.
Is cost of goods sold the same as my fees and postage?
The page does not include platform fees, postage or packaging, because it only adds the stock figures you enter. If you want those costs in the same picture, the selling price calculator and the ledger show profit per item after fees and postage.
How does cost of goods sold affect gross profit?
Gross profit is sales minus cost of goods sold. With $10,000.00 of sales and $6,100.00 of cost of goods sold, it is $3,900.00. Fees, postage and other expenses come off after that.
What is a good cost of goods sold to sales ratio?
The ratio is cost of goods sold divided by sales: $6,100.00 over $10,000.00 is 61%. No figure suits every seller, so compare yours with your own earlier years.
Does this connect to my eBay account?
No. You enter the figures from your own records, and your input stays in your browser. The page is not tax or legal advice.
Checked 3 November 2026 against the IRS Instructions for Schedule C (2025 edition), Part III, cost of goods sold.
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- Reseller Profit Calculator: to work out the profit on a lot you bought.
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