The seller’s reference desk

Ecommerce seller guides.
Fees, pricing and profit.

Clear explanations of marketplace fees, pricing, and profit. Find the details, then put them to work.

Amazon seller toolkit

Keep the numbers connected

FBA size tier checker Check your packaged size, shipping weight and seasonal fee. FBA fee & profit calculator Test one product’s price, fees and take-home profit. Fee Preview audit Find weak-margin SKUs in your own Amazon report.

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Shopify Plans 2026: Basic vs Grow vs Advanced (Which One?)

Side-by-side comparison of Shopify Basic, Grow, and Advanced plans for 2026. Real break-even math, verified card rates, and which plan wins at each GMV tier.

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Amazon FBA Fees Breakdown 2026 — Every Charge Explained

2026 US Amazon FBA fees: referral, fulfillment, storage, fuel surcharge and holiday costs. Rates checked September 26; guide updated September 27.

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Dropshipping vs Inventory on Shopify: Profit Comparison for 2026

Compare dropshipping and owned inventory on Shopify: supplier costs, shipping, returns, advertising, working capital, and worked profit examples.

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Etsy Fees Explained — What You Actually Pay in 2026

Understand US Etsy listing, transaction, processing, Offsite Ads, and refund fees. Official sources and a worked order example show what you keep in 2026.

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How to Calculate Profit Margin — Formula, Examples, and Common Mistakes

Step-by-step profit margin formulas for online sellers — gross margin, net margin, markup vs margin — with realistic Etsy, Shopify, and Amazon FBA examples.