The SKU-Level Profitability Problem
Most online sellers operate with a critical blind spot: they know their total company profitability but not their individual SKU profitability. A seller with 50 products might see 25% overall profit margin and assume all products are healthy—until they drill down and discover 10 products are actually unprofitable, subsidized by 5 star performers generating 60%+ margins. Multi-SKU tracking reveals which products truly drive profits and which drain resources, enabling data-driven decisions about pricing, inventory, marketing, and even which products to discontinue.
Without SKU-level profitability analysis, sellers make costly mistakes: keeping unprofitable products in inventory, advertising losers at the expense of winners, and misallocating limited capital. This comprehensive guide covers the SKU tracking foundation, data collection methods, profitability calculations for each product, and actionable strategies to optimize your entire product portfolio.
Understanding SKU: Stock Keeping Unit
A SKU (Stock Keeping Unit) is a unique identifier for each distinct product or product variant you sell. For example, a blue t-shirt in size M is one SKU; the same shirt in size L is a different SKU. Each SKU gets its own tracking, inventory count, cost basis, and pricing. This granular tracking enables accurate profit calculations for each individual product variation.
Some sellers confuse products with SKUs. A product is the general item (blue t-shirt); SKUs are the specific variants (blue t-shirt size S, blue t-shirt size M, blue t-shirt size L, blue t-shirt size XL). For profitability tracking, you analyze at the SKU level, not the product level, because each SKU has unique costs and margins.
The SKU-Level Profitability Formula
Revenue Per SKU − COGS − All Fees − Allocated Advertising = Net Profit Per SKU
Each component requires careful data collection and allocation:
Revenue Per SKU
Track total sales revenue for each SKU after returns, refunds, and discounts. Use your platform's reporting (Amazon Seller Central, Shopify analytics, etc.) to pull SKU-specific revenue. Don't use gross revenue; use net revenue after customer returns.
COGS (Cost of Goods Sold)
This is your cost to acquire/make each unit. Calculate landed cost per SKU: supplier price + inbound shipping + tariffs + packaging + prep costs. If you source from multiple suppliers or receive shipments at different prices, calculate a weighted average landed cost per SKU.
All Fees
Collect platform-specific fees: referral fees (usually 8-15%), fulfillment fees (FBA or your own shipping), payment processor fees, transaction fees, and any refund/return processing fees. Allocate these per SKU based on that SKU's revenue.
Allocated Advertising
If you run ads, allocate advertising spend to SKUs. Don't treat advertising as a company-wide expense; assign each SKU its proportional advertising cost based on actual spend driving that SKU's sales.
Step-by-Step SKU Tracking Implementation
Step 1: Assign Unique SKUs to All Products
Create a consistent SKU naming convention. Examples: TSHIRT-BLUE-S, TSHIRT-BLUE-M, TSHIRT-RED-S, etc. Or use numeric codes: 001001, 001002, etc. Ensure every product listing uses its unique SKU across all sales channels (Amazon, Shopify, Etsy, your website).
Step 2: Collect Revenue Data by SKU
Export transaction reports from each sales platform showing revenue by SKU. Most platforms provide this natively: Amazon Seller Central's Transaction reports, Shopify analytics, Etsy Stats. Consolidate this data into a master spreadsheet or accounting software.
Step 3: Calculate Landed Cost Per SKU
For each SKU, calculate total landed cost: supplier cost + inbound shipping/tariffs + packaging. Divide total landed cost by units received. This is your COGS per SKU. If sourcing from multiple suppliers, calculate a weighted average.
Step 4: Allocate Platform Fees by SKU
Extract fee data from your platform. If Amazon charged you $10,000 in fees across 100 SKUs totaling $100,000 in revenue, average fee is 10% of revenue. Apply this percentage to each SKU's revenue (or use platform-specific rates if they vary by category).
Step 5: Allocate Advertising Spend by SKU
If running ads, most platforms show ad spend by SKU or ASIN. Allocate proportionally: if SKU-A generated $10,000 revenue from $2,000 ad spend (20% ACOS), allocate $2,000 advertising cost to SKU-A. Don't use company-wide average; use actual spend per product.
Step 6: Calculate Net Profit Per SKU
For each SKU: Net Profit = Revenue − COGS − Fees − Advertising. Track this monthly or quarterly. Create a dashboard showing profit per SKU, profit margin percentage, and ranking.
Real Example: Multi-SKU Analysis
Company selling phone cases on Amazon with 5 SKUs:
| SKU | Revenue | COGS | Fees (12%) | Ads | Net Profit | Margin % |
|---|---|---|---|---|---|---|
| Case-Black-XL | $25,000 | ($6,250) | ($3,000) | ($2,500) | $13,250 | 53% |
| Case-Blue-XL | $18,000 | ($4,500) | ($2,160) | ($1,800) | $9,540 | 53% |
| Case-Red-XL | $12,000 | ($3,600) | ($1,440) | ($2,400) | $4,560 | 38% |
| Case-Clear-S | $8,000 | ($4,000) | ($960) | ($1,200) | $1,840 | 23% |
| Case-Pattern-S | $5,000 | ($3,500) | ($600) | ($1,500) | ($600) | -12% |
| TOTAL | $68,000 | ($21,850) | ($8,160) | ($9,400) | $28,590 | 42% |
In this example, the company's overall 42% margin masks a serious problem: one SKU (Case-Pattern-S) is unprofitable at -12%, generating losses instead of profit. Without SKU-level analysis, this loss was hidden in the overall 42% average. With it, management can decide to: raise the pattern case price 15%, cut advertising spend, or discontinue it entirely.
Identifying High-Performing vs. Underperforming SKUs
Star Products (40%+ margin): Invest here. Increase advertising, improve listing quality, and scale inventory. These products fund the business.
Strong Products (25-40% margin): Maintain these. They're healthy and stable. Optimize them cautiously.
Weak Products (10-25% margin): Analyze carefully. Can you raise prices? Reduce COGS? Cut advertising waste? These need attention.
Loss Products (below 10% or negative): These are money losers. Either fix them (raise price 15-20%, reduce costs, cut bad ads) or discontinue. Continuing to sell a product that loses money is worse than not selling it.
Post-Advertising Gross Profit (PAG) Analysis
Industry standard metric for SKU profitability is PAG (Post-Advertising Gross Profit). This is profit AFTER all advertising spend:
PAG = (Revenue − COGS − Fees) ÷ Revenue
For profitable products, target PAG of 40%+. PAG below 20% indicates the product struggles to cover advertising costs. Sellers benchmark products at:
- Excellent: 45%+ PAG (strong products worth scaling)
- Good: 35-45% PAG (healthy products)
- Acceptable: 25-35% PAG (marginal but viable)
- Concerning: 15-25% PAG (needs attention)
- Danger: Below 15% PAG (likely unprofitable with advertising)
Tools for SKU-Level Tracking
Spreadsheets (Google Sheets, Excel)
Build custom SKU tracking in a spreadsheet. Download platform data, calculate COGS/fees/advertising per SKU, and create formulas for profitability. Free but time-consuming and error-prone as complexity grows.
Accounting Software (QuickBooks, Xero)
Track profitability by product/SKU. Integrate with Amazon, Shopify, etc. for automatic data sync. Better accuracy than spreadsheets but requires proper setup.
SKU Analytics Tools (Seller Labs Data Hub, Teikametrics, Pacvue)
Specialized tools for SKU profitability. Pull data from all channels, calculate profitability automatically, create dashboards. Most expensive but most accurate and automated.
Platform Native Tools (Amazon FBA Revenue Calculator, Shopify Analytics)
Free tools within each platform. Limited but useful for quick per-SKU checks. Use as a starting point, then migrate to more comprehensive tracking.
Common SKU Tracking Mistakes
Using company-wide average fees instead of SKU-specific: Categories have different fee rates. Electronics have different referral fees than clothing. Use actual rates per SKU.
Not allocating advertising by SKU: Treating ads as an overhead expense instead of allocating to specific SKUs distorts profitability. Every ad dollar should attach to the SKU it promotes.
Using FOB price instead of landed cost: Landed cost (including inbound shipping, tariffs, packaging) is the true COGS. FOB-only calculation understates costs by 20-30%.
Forgetting to account for returns: If 10% of SKU-A's sales are returned, revenue should reflect this. Use net revenue after returns, not gross sales.
Not updating SKU costs quarterly: Supplier prices, freight rates, and advertising efficiency change. Recalculate profitability quarterly to stay current.
Optimizing Portfolio with SKU Data
Raise prices on high-margin SKUs: If SKU-A has 50% PAG, a 5% price increase likely increases profit 10-15% (since margin is high, elasticity is lower). Test carefully.
Reduce advertising on low-ROAS SKUs: If an SKU generates $2 revenue per $1 advertising spend (2 ROAS), but PAG is only 18%, that product is barely profitable even with sales. Cut ads or discontinue.
Consolidate inventory: Slow-moving SKUs tie up cash and accumulate storage fees. Focus inventory on fast-moving winners.
Bundle underperformers with winners: Bundle a 15% margin SKU with a 50% margin SKU at a bundled price between individual prices. This moves inventory and improves overall profitability.