Cost of Goods Sold Explained for Small Businesses
If you sell physical products, one number tells you more about your pricing than almost any other: cost of goods sold, or COGS. It is the direct cost of the items you actually sold, and it sits right below revenue on your profit and loss statement. This guide explains the formula, what belongs in COGS and what does not, and how to use it to check whether your prices are really working.
Key takeaways
- COGS = beginning inventory + purchases minus ending inventory.
- It includes the direct costs of making or buying what you sold, not general overheads like marketing or office rent.
- Revenue minus COGS gives you gross profit, the money left to pay for everything else.
- An accurate year-end stock count is essential, because ending inventory directly changes your COGS.
- Tracking COGS monthly helps you spot rising supplier costs before they eat your margin.
Plenty of small business owners look at sales, then at the bank balance, and try to work out what happened in between. Cost of goods sold is the missing link. It separates the cost of your products from the cost of running the business, so you can see whether each sale is actually profitable before overheads come into play.
Late January is a natural moment to get to grips with COGS. The holiday rush is over, your year-end stock count is fresh, and your accountant is probably asking for inventory figures. Understanding the number now makes this year's tax return easier and next year's pricing smarter.
A quick note: this article is general information about accounting concepts, not tax or accounting advice. How you calculate and report COGS depends on your country, business structure and accounting method, so check with a qualified accountant.
What cost of goods sold means
Cost of goods sold is the total direct cost of the products you sold during a period, such as a month, a quarter or a year. "Direct" is the key word. It covers what it took to buy or make the goods, not what it took to market them or keep the lights on in your office.
Think of a candle maker. The wax, wicks, jars, fragrance and labels in each candle she sold are part of COGS. Her website subscription, her accountant's fee and her Instagram ads are not. They are operating expenses, and they show up further down the profit and loss statement.
Why it matters
- It shows your gross profit. Revenue minus COGS tells you how much each sale contributes before overheads.
- It drives pricing decisions. If COGS rises and your prices do not, your margin shrinks quietly.
- It affects your tax bill. In many tax systems, COGS reduces taxable profit, so getting it right matters.
- It reveals inventory problems. Unexplained jumps in COGS can point to waste, theft or counting errors.
The COGS formula
The standard formula uses three numbers you can find in your records.
- Beginning inventory is the value of stock you had at the start of the period. It is usually last period's ending inventory.
- Purchases are the direct costs of stock you bought or made during the period.
- Ending inventory is the value of stock still on hand at the end of the period, based on a count.
The logic is simple. Everything you had available to sell is beginning inventory plus purchases. Whatever is still on the shelf at the end was not sold. The difference is what went out the door, valued at cost.
Worked example
Imagine Maya runs a small online shop selling handmade ceramics. On 1 January last year, her stock was worth $4,000 at cost. During the year she spent $18,000 on clay, glazes, packaging and kiln firing. Her year-end count values the remaining stock at $5,500. Her COGS is $4,000 + $18,000 minus $5,500, which equals $16,500. If her sales for the year were $42,000, her gross profit is $42,000 minus $16,500, or $25,500. (All figures are made up for illustration.)
What to include in COGS, and what to leave out
This is where most confusion happens. The exact rules depend on your tax system and accounting method, but these general guidelines cover most small product businesses.
Usually included
- The purchase price of goods you buy to resell
- Raw materials and components for products you make
- Shipping and freight costs to bring stock in to you
- Packaging that is part of the product
- Direct labor spent making the product, in some businesses
- Some production overheads, such as factory or workshop costs, depending on your method
Usually left out
- Marketing, advertising and sales commissions
- Office rent, admin salaries and general utilities
- Software subscriptions not used in production
- Shipping costs to send orders to customers, which many businesses treat as a selling expense
- Professional fees, insurance and bank charges
Common mistake
Putting every purchase into COGS. If you include ads, software and rent, your gross margin looks terrible and your operating expenses look tiny, which makes both numbers useless for decisions. Keep COGS for direct product costs only, and agree the boundary with your accountant so it stays consistent year to year.
What about service businesses?
Pure service businesses, like consultants or designers, often have no inventory and may not report COGS at all. Some prefer to track a "cost of services" or "cost of revenue" line for direct costs such as subcontractors working on client projects. It is not the same as COGS in a tax sense, but the idea of separating direct costs from overheads is just as useful.
Counting and valuing your inventory
Because ending inventory is subtracted in the formula, it has a big effect on COGS. Overcount your stock and COGS looks too low, making profit look higher than it really is. Undercount and the opposite happens.
- Pick a count date that matches the end of your accounting period, often the last day of the year.
- Count everything physically: shelves, storage, items in transit you already own and stock held by others for you.
- Value each item at cost, not at selling price. Use your supplier invoices or production cost records.
- Write down damaged or unsellable stock separately, and ask your accountant how to treat it.
- Reconcile with your system if you use inventory software, and investigate big differences.
- Save the count sheet with your tax records for the year.
Inventory valuation methods
When the price you pay for stock changes over the year, you need a method for deciding which costs belong to the items you sold. Common methods include:
- FIFO (first in, first out): assumes the oldest stock sells first. It is widely used and easy to understand.
- Weighted average cost: spreads the total cost evenly across all units available.
- Specific identification: tracks the actual cost of each item, practical for unique or high-value goods.
- LIFO (last in, first out): assumes the newest stock sells first. It is allowed in some US situations but not under many other accounting standards.
The method you choose can change your COGS and taxable profit, and switching later may need permission or adjustments. Ask your accountant which methods are allowed for your business and stick with one.
Pro tip
Count slow-moving stock at the same time and note how long it has been sitting there. That list is the starting point for a clearance sale and for smarter buying next year.
Using COGS to check your margins
COGS becomes really useful when you turn it into ratios you can track month to month.
Gross margin
Gross margin is gross profit divided by revenue, shown as a percentage. In Maya's example, $25,500 divided by $42,000 is about 61%. If that figure drifts down over several months, either costs are rising or discounts are eating into prices.
Inventory turnover
Inventory turnover shows how many times you sell through your stock in a period. The formula is cost of goods sold divided by average inventory. Maya's average inventory is ($4,000 + $5,500) divided by 2, or $4,750, so her turnover is $16,500 divided by $4,750, about 3.5 times a year. Higher turnover usually means less cash tied up on shelves, though the right level depends on your industry.
COGS tracker template
Copy this into a spreadsheet and update it monthly or quarterly. The numbers are made-up examples to show how the columns fit together.
| Period | Beginning inventory | Purchases | Ending inventory | COGS | Revenue | Gross margin |
|---|---|---|---|---|---|---|
| Q1 (example) | $4,000 | $4,200 | $4,400 | $3,800 | $9,500 | 60% |
| Q2 (example) | $4,400 | $4,600 | $4,700 | $4,300 | $10,400 | 59% |
| Q3 (example) | $4,700 | $4,100 | $4,500 | $4,300 | $10,000 | 57% |
In this example, the margin slips from 60% to 57% over three quarters. That is a signal to check supplier prices, waste and discounting before it becomes a bigger problem.
Common mistake
Pricing from the purchase price alone. If you forget freight-in, packaging or materials lost to breakage, your true COGS is higher than you think, and every sale is less profitable than it looks. Build all direct costs into your per-unit cost before setting prices.
Your COGS action plan
- Find last year's beginning inventory value
- Total your direct purchases for the year, including freight-in and packaging
- Complete a year-end stock count and value it at cost
- Calculate COGS with the formula and check it with your accountant
- Work out gross profit and gross margin
- Calculate inventory turnover and list slow-moving stock
- Set up the COGS tracker and update it monthly or quarterly
- Review prices for any product whose margin has slipped
Frequently asked questions
Is COGS the same as operating expenses?
No. COGS covers the direct cost of the goods you sold. Operating expenses cover running the business, such as rent, marketing and admin. Keeping them separate shows whether problems come from your product costs or your overheads.
Do I need to calculate COGS if I sell on a marketplace?
If you hold inventory, generally yes. Marketplace fees are usually treated as selling expenses, while the cost of the products themselves goes into COGS. Check with your accountant how to treat platform and fulfillment fees.
How often should I count inventory?
At least once a year for your accounts. Many small shops also do quick monthly or quarterly counts of their top products, which keeps records accurate and catches problems early.
Can COGS be higher than revenue?
It can happen, for example after heavy discounting or a big stock write-off. If it continues, the business is losing money on every sale, and pricing or sourcing needs urgent attention.
Related reading
The bottom line
Cost of goods sold is simply what it cost you to buy or make what you sold: beginning inventory plus purchases minus ending inventory. Keep it limited to direct product costs, count your stock carefully, and turn the result into gross margin and inventory turnover you can track over time.
Use this month's stock count to calculate last year's COGS, then set up the tracker for 2027. A few minutes each quarter will tell you whether your prices are still doing their job.
