Sources

Where our numbers come from.

Trust the math. Check the math.

OptiSKU's rates, rules and benchmarks come from official sources first: US Customs, the US International Trade Commission, the US Trade Representative and the International Chamber of Commerce. Industry research and practitioners fill in what governments don't publish. Each is listed with what we use it for.

Duty, tariffs and customs value

Duty rates, how the value you pay duty on is worked out, and the added tariffs in force in 2026.

• Harmonized Tariff Schedule of the United States · U.S. International Trade Commission
  The official US tariff schedule: every HTS code and its general duty rate.
• 19 CFR 152.103, Transaction value · Code of Federal Regulations
  How US Customs values imports: the price paid, plus additions like assists (molds and dies you supply), and excluding ocean freight and insurance.
• Valuation Encyclopedia · U.S. Customs and Border Protection
  CBP's summary of its rulings on customs value, including assists and tooling.
• USTR Takes Action in Forced Labor Section 301 Investigations (July 2026) · Office of the U.S. Trade Representative
  The announcement of added tariffs of 10% or 12.5% on goods from 60 economies.
• Notice of Actions in Section 301 Investigations (July 28, 2026) · Federal Register
  The legal notice with the economies, rates and effective date.

Shipping terms and freight

What FOB and DDP mean, and what ocean freight costs right now.

• Incoterms® rules · International Chamber of Commerce
  The official rules behind FOB, DDP, EXW and other shipping terms. Incoterms® 2020 is the current edition.
• World Container Index · Drewry
  Weekly spot ocean freight rates per 40-foot container on the main East–West routes.

Retail math and buying

Markup, margin, IMU, markdowns, open-to-buy and sell-through targets.

• Mathematics for Retail Buying (Fairchild Books) · Bette K. Tepper and Newton E. Godnick
  The standard textbook for retail math: markup, margin, IMU, markdowns and open-to-buy.
• Ronnie Fieg on Kith's 15-Year Evolution (September 2026) · Complex
  Kith's founder on buying to an 85–90% sell-through target and reported margins on brands it buys wholesale.

Industry outlook

Where the market is heading, used for growth checks in the plan.

• The State of Fashion 2026 · McKinsey & Company and The Business of Fashion
  The industry's annual outlook, built from executive surveys and market data. Expects low single-digit growth in 2026.

Footwear tooling

What molds cost, and how US Customs treats molds you pay for.

• How much does it cost to build a sneaker? · Shoemakers Academy (Wade Motawi)
  Mold and tooling costs from a footwear developer with 30+ years in Asian factories.
• Cost to Make Shoes in China · TLSTAGE
  A sourcing agent's breakdown of outsole mold costs per size and total tooling budgets.
• 19 CFR 152.103, Transaction value · Code of Federal Regulations
  How US Customs values imports: the price paid, plus additions like assists (molds and dies you supply), and excluding ocean freight and insurance.

How we use them

• Official sources win. Where a government source and an industry guide disagree, OptiSKU follows the government source.
• Estimates are labeled. Customs codes, duty rates and tooling costs in OptiSKU are planning estimates, not rulings or quotes.
• Checked regularly. Last full check: October 2026. Tariffs in particular change often and are being challenged in court.

OptiSKU isn't affiliated with any source listed here. Spotted something out of date? Tell us through the contact form.