Cost of goods sold: What it is, how to calculate it, and why it changes how you price

Two businesses can have identical revenue and completely different financial situations. An illustrative hardware store that brings in $400,000 a year and spends $280,000 on the products it sells earns $120,000 in gross profit, which is a 30% gross margin. A consulting firm with the same revenue and no merchandise inventory faces a different cost structure entirely. The first line that makes those two businesses look different on the income statement is the cost of goods sold.

For any business that sells physical products, or that has direct costs tied to delivering specific services, cost of goods sold is one of the most important numbers on the financial statements, and one of the most frequently miscalculated.

What cost of goods sold actually includes

Cost of goods sold is the cost assigned to the inventory sold during the accounting period. For a product business, that includes the purchase cost of merchandise, production or conversion costs for manufactured goods, and other qualifying costs of bringing inventory to its present location and condition. Describing COGS as only "direct costs" is incomplete for manufacturing businesses, because manufacturing inventory also includes appropriately allocated indirect production costs such as factory supervision, utilities, and machinery depreciation.

For a service business, the equivalent is sometimes called cost of revenue or cost of services. It includes resources directly used to deliver specific engagements: subcontractors on particular projects, materials consumed in service delivery, and wages of staff who perform the actual service work. General overhead of running the business belongs in operating expenses, not cost of services.

The inventory formula and why purchases are not the same as COGS

For a retailer, the COGS calculation starts with beginning inventory, adds net purchases during the period, and subtracts ending inventory. The IRS's fuller calculation adds applicable labour, materials and supplies, and other costs before subtracting ending inventory. A manufacturer must account for the relevant production costs, not just purchases of finished merchandise.

Net purchases matter as a concept. Purchase returns and allowances reduce the purchases figure. Trade discounts reduce acquisition cost. Qualifying acquisition costs such as freight-in must be captured. Merchandise taken for personal use does not belong in the cost of goods sold to customers.

Assume the illustrative paint supply retailer has no inventory losses or other adjustments:

The business assigns $23,000 of inventory cost to the goods it sold. The remaining $7,000 stays in inventory rather than becoming COGS simply because the business bought it. Accurate COGS depends on accurate ending inventory. If ending inventory is not counted or valued correctly, COGS is wrong, and the error flows directly into gross profit and net income.

FIFO and weighted average: correcting the unit example

When identical products are bought at different prices over time, the business needs a consistent rule for assigning costs to units sold and units remaining. Two widely used methods are FIFO and weighted average.

FIFO assigns older costs first. Weighted average blends costs of comparable units. IAS 2 permits both methods for ordinarily interchangeable inventory and does not generally require one over the other. The IRS also recognises both methods, along with others, requiring consistent application once a method is adopted.

The illustrative business buys 100 units at $10 and then 100 units at $12, then sells 80 units after both purchases. The total acquisition cost available is $2,200. The methods divide that same total differently:

An important correction from the original blog: FIFO ending inventory does not consist only of the $12 batch. Because only 80 of the original 100 units at $10 were sold, 20 units from that first batch remain. Both methods reconcile to the same $2,200 total acquisition cost, just divided differently between the income statement and the balance sheet.

In this rising-cost example, FIFO produces lower COGS and higher gross profit than weighted average with identical revenue. That is an accounting allocation difference, not evidence that one method is more accurate than the other.

The IRS requires consistent use of the chosen inventory method across periods. Changing from one method to another is an accounting method change requiring IRS approval through Form 3115, the same process described in the cash-to-accrual blog. Selecting a method that fits the business and applying it consistently is the practical priority.

Gross margin and markup: they are not the same calculation

The original blog presented gross margin without distinguishing it from markup, and the distinction matters for pricing. Confusing the denominators causes a price to miss its intended margin.

Gross profit = revenue minus COGS Gross margin (%) = (gross profit divided by revenue) times 100 Markup (%) = (gross profit divided by cost) times 100

For the paint retailer with $60,000 in monthly revenue and $23,000 in COGS, gross profit is $37,000 and gross margin is approximately 61.7%. That is not net profit margin: operating expenses, taxes, and other charges still reduce the remaining amount.

At the unit level, the difference between margin and markup is illustrated by a simple case. Assume a unit cost of $30:

The instruction "add 40%" does not produce a 40% margin. It produces a 28.6% margin, because the denominator is cost rather than selling price. A business that intends a 40% margin and instead adds a 40% markup to cost will systematically undercharge. When cost rises, the problem compounds: a unit that cost $30 priced at $50 for a 40% margin now costs $36, and the same $50 price delivers only a 28% margin. The correct adjustment requires recalculating the required selling price, not simply noting that the cost increased.

Classification errors and owner draws

COGS should not become a catch-all for every business expense. General marketing, administrative salaries, office rent, and costs unrelated to production or service delivery belong in operating expenses. That said, manufacturing overhead is a legitimate inventory cost, and some service-delivery facilities or technology costs may properly belong in cost of services. The test is function, not expense name.

Owner withdrawals require a specific correction. An owner's draw is not COGS and is not an operating expense. It reduces equity. A sole proprietor cannot deduct their own salary or personal withdrawals as a business expense. Corporate payroll arrangements are different and require entity-specific treatment, but the baseline principle is that taking money out of the business as an owner is an equity transaction, not a cost of producing goods or operating the business.

Misclassifying overhead as COGS understates gross margin without changing total net income, because the same amount appears somewhere in the expense structure either way. But the distortion affects pricing decisions and margin analysis. The original example of $4,000 of administrative overhead included in COGS illustrates this:

Net income is identical. Gross margin is not. A business pricing based on 55% gross margin when the true margin is 61.7% is making decisions from a distorted picture of its product-level economics.

Federal tax reporting: Schedule C, Form 1125-A, and service businesses

The IRS generally allows the cost of goods sold to be subtracted from gross receipts when computing business income for businesses that make, buy, or sell goods to produce income. The calculation appears in different places depending on the return:

Schedule C's Part III calculation includes beginning inventory, purchases adjusted for personal withdrawals, applicable labour, materials and supplies, other costs, and ending inventory. Corporations and partnerships use Form 1125-A. The underlying cost records are the same; the form just formats them for the applicable return type.

An important distinction for service businesses: the IRS's inventory COGS guidance generally does not apply to personal-service businesses. A management cost-of-services calculation can be useful for understanding which engagements are profitable, but that internal analysis does not automatically translate into a deductible COGS line on the tax return. Confirm with your accountant whether your business's delivery costs qualify as COGS for tax purposes or are more appropriately reported as ordinary business expenses.

How Inkle helps

Inkle Books tracks revenue and expenses monthly as part of the close, with professional bookkeepers ensuring that COGS and operating expenses are correctly separated in the chart of accounts. For product businesses, the account structure maintains beginning inventory, purchases, and ending inventory inputs to produce an accurate COGS figure each period. For service businesses, the same structure separates direct delivery costs from overhead.

Inkle Tax prepares federal, state, and franchise filings from the same underlying records. For businesses with inventory, the COGS figure on Schedule C or Form 1125-A comes from the maintained bookkeeping records rather than from a separate year-end calculation, which keeps the books and the return consistent and reduces the risk of errors that create audit exposure.

Inkle handles bookkeeping and tax for owner-operated businesses across the US. See how it works or book a demo to talk through what your business needs.