A product business can sell more and still wonder where the money went. One common reason is that the cost attached to each sale is incomplete. Materials are counted, but incoming freight, production labor, failed units, or packaging are scattered across other expense categories.
Reliable COGS tracking for product creators connects what was sold with what it actually cost to make or acquire. It supports pricing, product decisions, and cleaner conversations with a bookkeeper. It is also different from simply totaling every purchase made this month.
Understand what COGS is measuring
Cost of goods sold, or COGS, represents the cost of inventory that was sold during a period. A basic calculation is:
Beginning inventory + inventory purchases or production costs − ending inventory = COGS
If a studio begins the month with $8,000 of inventory, adds $5,000 of eligible costs, and ends with $6,500, monthly COGS is $6,500. Revenue minus COGS produces gross profit. Gross profit divided by revenue gives gross margin percentage.
The timing matters. Buying $2,000 of jars does not necessarily create $2,000 of COGS that day. Unsold jars remain inventory. Their cost moves into COGS when the products containing them are sold, subject to the business’s accounting method and applicable tax rules.
This article is operational guidance, not tax advice. Inventory accounting choices can affect taxable income, so confirm treatment with a qualified accountant and apply it consistently.
Build a complete product cost
Direct materials and packaging
Start with the approved bill of materials or recipe for one saleable unit. Include ingredients, components, primary packaging, labels, inserts, closures, and other items that physically become part of the product.
Use the landed cost of materials rather than the supplier’s unit price alone. Allocate inbound freight, duties, and other acquisition costs with a consistent method. If 1,000 bottles cost $800 plus $200 freight, the useful starting cost is $1 per bottle, not 80 cents.
Unit conversions need special attention. A maker may buy oil by the gallon and use it by the ounce, or buy labels by the roll and issue them individually. Record both the purchasing unit and production unit, then verify the conversion with a small test.
Direct production labor
Time the work required to make the product: setup, weighing, mixing, forming, filling, labeling, and product-specific cleanup. Multiply the time by a sustainable labor rate, including relevant payroll burden when appropriate.
Founder labor should not disappear because no paycheck was issued for that batch. Recording it reveals whether the product can support a future employee or contract maker. Keep general administration, marketing, and unrelated customer service separate unless your accountant directs otherwise.
Yield loss and normal waste
A formula may be designed for 100 units but produce only 92 acceptable units after transfer loss, evaporation, breakage, test samples, and rejects. Divide total batch cost by acceptable output—not theoretical output.
Suppose materials, packaging, and direct labor total $460. If the run yields 92 saleable units, unit production cost is $5. If you divide by the planned 100, the stated cost is $4.60 and every margin calculation begins 40 cents too optimistically.
Record unusual loss separately. A spill caused by a broken tool deserves investigation; burying it in a permanent waste allowance makes the process problem invisible.
Keep product cost separate from period expenses
COGS is not the same as every cost of operating the company. Website hosting, advertising, professional fees, office supplies, and most general administrative work are typically operating expenses. Rent, utilities, equipment depreciation, and production supervision may require an allocation method depending on how the business accounts for inventory.
The classification can be nuanced. Create a written cost policy with your accountant rather than moving expenses in and out of COGS whenever the result looks better. The policy should state which costs are included, how shared costs are allocated, and how often standards are updated.
For management decisions, you can also maintain a contribution view that subtracts channel-specific variable costs such as payment fees, marketplace commissions, and shipping subsidies. Label it clearly. This is useful for pricing, but it should not be confused with the official COGS reported in financial statements.
Connect batches, inventory, and sales
A practical tracking system has three linked records:
- Material receipt: item, quantity, unit, landed cost, supplier, and date.
- Production record: product version, actual materials used, labor, yield, waste, and finished quantity.
- Inventory movement: quantities completed, adjusted, damaged, transferred, and sold.
Without these links, month-end costing becomes a reconstruction exercise. A purchase spreadsheet may know that wax arrived, while a production notebook knows what was poured and an ecommerce platform knows what sold. No single record explains the change in inventory value.
Record transactions close to the work. A simple weekly routine is better than a sophisticated sheet updated from memory at quarter-end. Limit who can alter approved formulas and prior-period costs, and preserve an explanation for corrections.
Reconcile the records monthly
Start with a physical count for high-value and high-use items. Compare quantities with the system, investigate differences, and record approved adjustments. Common causes include unrecorded samples, damaged packaging, unit conversion errors, and production output entered late.
Then review three reports together:
- COGS and gross margin by month;
- expected versus actual batch yield;
- unit cost and contribution by product or product family.
Investigate changes rather than automatically accepting them. A lower gross margin could reflect a supplier increase, heavier discounts, a product mix shift, freight, inaccurate counts, or a formula change. The total alone cannot identify the cause.
Use a closing checklist: enter all receipts, complete open production records, count priority inventory, approve adjustments, update eligible costs, and lock the period after review. Reopening a period should require a documented reason.
Avoid common COGS mistakes
Do not use the latest ingredient price for every historical sale. Do not count a material purchase as both inventory and an immediate expense. Do not ignore packaging because it is inexpensive per piece; thousands of small omissions become meaningful. Do not use planned yield when actual output is available.
Also avoid excessive precision unsupported by the process. If production usage is estimated and counts are irregular, a unit cost with six decimal places is not more accurate. Improve the underlying records first.
Kerno can help connect formulas, material costs, production runs, yield, and inventory movements for ongoing product costing. The business still needs a clear cost policy, disciplined entries, and periodic accounting review.
Take one product from purchase to sale
Choose a high-revenue SKU and trace one recent batch. Verify the landed cost of each material, labor time, actual yield, finished quantity, and units sold. Compare the reconstructed unit cost with the number currently used for pricing.
If the numbers differ, write down why before changing anything. That short exercise often exposes the most valuable next improvement: a missing packaging cost, an unreliable conversion, unrecorded waste, or an inventory count that has not been reconciled. Accurate COGS begins with one complete path, repeated consistently.
