Where our numbers come from

Year-over-year diff Amazon publishes when rates change; useful for the 'why did my fee go up?' question.

https://sellercentral.amazon.com/help/hub/reference/external/G201411300

How Amazon decides which category your product belongs in — relevant when a listing falls between two categories.

https://sellercentral.amazon.com/help/hub/reference/external/GFD6HLGAEZC9VBGJ

Per-unit fee Amazon charges when sellers split inventory across fewer fulfillment centers than Amazon prefers. Source of the rate card encoded in `src/lib/calc/fees/us-ips-2026.ts`. Updated 2026-01-15: Standard rates raised ~$0.05/unit, Bulky split into Small Bulky / Large Bulky, weight bands added to Large Standard 3-20 lb.

https://sellercentral.amazon.com/help/hub/reference/GC3Q44PBK8BXQW3Z

Summary of the 2026 EU-wide fee cuts (Clothing, Home Products, Grocery, Pet, Vitamins). Background reading for why Q1 2026 rates are lower than 2025.

https://www.aboutamazon.eu/news/empowering-small-business/update-to-european-referral-and-fulfilment-by-amazon-fees-for-2026

Source of the size-tier rate table encoded in `src/lib/calc/fees/jp-2026.ts`. JP grades by sum-of-3-sides (Standard) or longest side (Oversize / Supersize), with weight as a per-band ceiling and two price columns (>¥1,000 vs ≤¥1,000). Fees include 10% consumption tax.

https://sell.amazon.co.jp/en/pricing#fba_nav_tag

JP storage rate is per litre × storage days. Non-apparel ≈ ¥160.71/cu ft/month Jan–Sep, ¥285.59 Oct–Dec; Clothing/Shoes/Bags ≈ ¥92.82 Jan–Sep, ¥197.71 Oct–Dec. These are encoded in `JP_STORAGE_RATE` and `JP_STORAGE_RATE_APPAREL`.

https://sell.amazon.co.jp/en/pricing#fba_nav_tag

Companion article documenting the Oct-31-2024 jewelry sub-type reduction (5% on Diamond / Gold / Jade / Platinum / Carat Gold / Ruby / Sapphire / Emerald).

https://seller-us.tiktok.com/university/essay?knowledge_id=5982454398175018&default_language=en

State-dependent sales tax applied on top of the referral fee. NOT modeled in our calculator today — surface this link in the UI so Pro sellers know to factor it in by hand.

https://seller-us.tiktok.com/university/essay?knowledge_id=1017269682849550&lang=en

Discounted 3% referral fee for 30 days for sellers who make their first sale within 60 days of onboarding. Useful 'is this rate even applicable to me?' context — also not modeled in the calculator today.

https://seller-us.tiktok.com/university/essay?knowledge_id=1557461786560302