QUICK ANSWER

The short version

Subtract cost of goods sold from net sales to get gross profit. Divide gross profit by net sales and multiply by 100 to get gross margin percentage. Use the same period and a consistent cost method for both figures. Gross margin excludes operating expenses such as rent, office payroll, interest and income tax, so it is not the same as net profit margin.

Gross profit and gross margin formulas

Gross profit is a dollar amount. Gross margin is that amount expressed as a share of net sales. Keep both: the percentage helps compare periods or products, while the dollar amount shows how much money remains to cover operating expenses.

Gross margin percentage(Net sales − Cost of goods sold) ÷ Net sales × 100

If net sales are $80,000 and cost of goods sold is $44,000, gross profit is $36,000 and gross margin is 45%.

Use net sales for the same reporting period

Start with a clearly defined sales figure. Net sales usually reflects the source system's treatment of discounts, returns and refunds. Do not mix gross sales from one report with net costs from another without reconciling the difference.

The reporting period must match. Comparing a month of cost with a quarter of sales produces a number that looks precise but has no useful meaning. Record the date range, currency, locations and source used for every margin calculation.

Calculate cost of goods sold consistently

For a product business, cost of goods sold is the recorded cost attached to the items sold during the period. A periodic accounting calculation begins with opening inventory, adds purchases and other eligible product costs, and subtracts ending inventory. Canadian businesses should follow the tax and accounting rules that apply to their circumstances and confirm classifications with a qualified professional.

The Canada Revenue Agency explains that inventory is used to calculate cost of goods sold and net income. Its T4002 guidance identifies opening inventory, purchases net of discounts and ending inventory as inputs to the calculation. Internal management reports may update more often, but they still need a consistent cost source.

Periodic cost of goods soldOpening inventory + Net purchases and eligible direct costs − Ending inventory

Opening inventory of $25,000 plus $70,000 of net purchases minus $29,000 of ending inventory gives $66,000 of cost of goods sold.

Know what the percentage does and does not include

The exact classification depends on the business and accounting policy. The important management control is consistency: document the definition, apply it across periods and disclose when it changes.

Typical gross-margin boundaries
Usually part of the calculationUsually outside gross margin
Net sales for the periodRent and general office costs
Recorded cost of products soldInterest and financing costs
Eligible freight or direct acquisition costs under the chosen policyIncome tax
Direct production costs where applicableOwner draws and unrelated overhead

Calculate product margin carefully

Product-level margin can reveal whether sales growth is coming from profitable items or low-margin volume. Use actual net selling price after item-level discounts and the best supported unit cost. Allocate shared costs only when the method is defensible and useful for the decision.

A product with a high margin percentage can still contribute little gross profit if it rarely sells. Review margin percentage alongside units sold, gross profit dollars, return rate and inventory carrying risk.

Unit gross margin(Net unit selling price − Recorded unit cost) ÷ Net unit selling price × 100

A product sold for $40 after discount with a $22 recorded cost has $18 of unit gross profit and a 45% unit gross margin.

Common gross-margin mistakes

  • Calling gross margin net profit or cash flow.
  • Using retail price instead of actual net sales after discounts and returns.
  • Leaving unit costs blank and treating the missing amount as zero.
  • Comparing locations that use different cost or refund definitions.
  • Averaging product margin percentages without weighting them by sales.
  • Changing inventory valuation or cost classifications without marking the break in comparability.

Turn margin into an operating question

When gross margin changes, split the problem before acting. Check selling-price changes, discount mix, product mix, supplier cost changes, returns and missing cost records. A single blended percentage cannot tell you which cause moved.

Vanteloq's current metric registry calculates source-backed gross profit as net sales less recorded cost of goods sold and gross margin as gross profit divided by net sales. It returns unavailable when required inputs are missing instead of substituting zero, and its contribution-after-labour measure remains separate from net operating profit.

Sources and further reading

These sources support the accounting, platform or technical boundaries discussed in this guide. They are not endorsements of Vanteloq.