Cost of Goods Sold (COGS): Calculation & Common Mistakes

Cost of Goods Sold (COGS) is the direct cost of producing or acquiring the goods a business sells — raw materials, manufacturing labour, packaging, freight inbound, and other costs directly attributable to creating each unit. For ecommerce brands, COGS is the foundation of unit economics: every margin calculation, every pricing decision, and every CAC payback model starts with knowing COGS accurately.

How COGS is calculated

COGS = Beginning Inventory + Purchases during the period − Ending Inventory

Or, for unit economics: COGS per unit = Total direct costs to produce or acquire the unit, including:

Raw materials or wholesale cost of the goods themselves.
Manufacturing labour directly tied to producing the goods.
Freight inbound: shipping cost from supplier to warehouse.
Import duties and tariffs.
Packaging materials attached to the product (primary packaging only — not marketing inserts).
Direct quality control costs.

What is NOT in COGS:

Marketing and advertising spend (separate line).
Fulfillment and shipping to customer (separate line, often called "variable fulfillment").
Warehouse rent and overhead (separate line).
Customer service costs (operating expense).
Salaries of non-production staff.

The line between COGS and operating expense matters because it directly affects gross margin and gross profit — the metrics most investors and lenders look at.

Why COGS matters for ecommerce

COGS determines gross margin, which determines almost every meaningful business decision: pricing, ad-spend tolerance, channel selection, product mix, and cash flow timing. Brands with weak COGS visibility (especially smaller brands using approximate numbers) consistently misjudge product profitability — which products are pulling weight and which are dragging margin down.

For Shopify brands specifically, COGS often gets reported as the wholesale or production cost only, missing freight, duties, and packaging. The omission can understate true COGS by 15–30%, dramatically affecting gross margin reports.

What counts as good COGS

COGS as a percentage of revenue (the inverse of gross margin) varies wildly by category:

Apparel: 25–40% of revenue is typical (60–75% gross margin).
Beauty and personal care: 15–30% (70–85% gross margin).
Food and beverage: 30–55% (45–70% gross margin).
Furniture and home goods: 35–60% (40–65% gross margin).
Electronics: 50–75% (25–50% gross margin).

The right benchmark is the brand's own trajectory and category-specific competitive context. Cross-category comparisons mostly aren't useful.

How to improve COGS

Negotiate volume pricing with suppliers. Per-unit cost typically declines materially at scale tiers (10K, 50K, 100K units). Brands that don't push for tiered pricing leave margin on the table.
Reduce freight and duty cost. Consolidate shipments, negotiate carrier contracts, audit Harmonized Tariff Schedule (HTS) classifications. HTS reclassification alone has saved many brands 5–15% on duties.
Audit packaging. Smaller, lighter packaging reduces both material cost and freight cost simultaneously.
Reformulate or redesign for cost. Ingredient or material substitutions that maintain quality while reducing cost. Sensitive territory — customer-perceived quality matters — but often a viable lever.
Consider direct sourcing. Brands buying from distributors can sometimes go direct to manufacturers, reducing markup tiers. Adds operational complexity.

Common COGS mistakes

Excluding freight, duties, and packaging from COGS. The most common error. Reported COGS understates true COGS, overstating gross margin.
Mixing COGS with fulfillment cost. Variable fulfillment (pick, pack, ship-to-customer) is operationally distinct from COGS. Conflating them obscures what's actually driving margin.
Static COGS in a changing supply chain. Costs change — raw materials, labour, freight all fluctuate. Brands that update COGS quarterly or less frequently miss material shifts.
Per-product averaging across SKUs with very different cost structures. Aggregate COGS hides which SKUs are profitable and which aren't.