Importing into the United States rarely costs just the duty rate on your invoice. Between Section 301 tariffs, anti-dumping orders, and the Merchandise Processing and Harbor Maintenance fees, the real number — your landed cost — can be meaningfully higher than the headline duty. This guide explains how each piece is calculated and how to find the figures you need.

Customs value: FOB vs CIF

FOB and CIF describe supplier pricing. Use the goods transaction value plus any applicable customs adjustments for U.S. customs value. Exclude separately stated international freight and insurance under either term and enter those costs separately for landed cost.

The customs value and the cash needed for this shipment answer different questions. For example, an allocated assist can increase dutiable value even when its purchase was paid elsewhere. Review the additional cash cost separately instead of counting the valuation adjustment twice. The ledger identifies the amount in the customs base and the amount in landed cost for each component. A documented inclusive invoice removes stated international freight and insurance from the duty base while retaining those costs once in the cash total.

Finding your HTS code and rate

Every product has a 10-digit Harmonized Tariff Schedule classification, published by the U.S. International Trade Commission at hts.usitc.gov. The HTS line gives you the general duty rate — most often an ad-valorem percentage, sometimes a specific duty per unit, occasionally both. Classification is the single biggest driver of duty and the most common source of error: a few digits can change the rate by double digits. When in doubt, a licensed customs broker or a CBP binding ruling settles the classification.

Section 301 and anti-dumping tariffs

Additional duties depend on the product, origin, producer, entry date and applicable official notices. Section 301 and anti-dumping or countervailing duties are distinct from ordinary base duty, and other additional duties can also apply. A zero base rate or an FTA selection does not establish exemption from those separate charges. The calculator applies the percentages you enter as assumptions; it does not determine active lists, exclusions or producer-specific rates. The generic additional-duty field assumes an ad-valorem charge on the same customs value. Do not use that field to certify a charge with a different base, specific amount or legal treatment. Confirm those cases separately.

MPF, HMF, and the de-minimis rule

Formal MPF is 0.3464% of customs value. The minimum and maximum are $33.58 and $651.50 for FY2026 and $34.58 and $670.86 for FY2027, beginning October 1, 2026. Informal MPF depends on the channel. HMF is 0.125% of qualifying commercial cargo value on ocean shipments. Use the entry date to select published FY2026 or FY2027 formal MPF limits. The model uses entered customs value for duty and user fees. HTS, origin and trade-program eligibility must be verified independently. No informal MPF or low-value exemption is calculated.

Compare both the total cash requirement and the cost per unit. A fixed fee can be diluted across more units, while an ad-valorem fee changes with value and can reach a minimum or maximum. The shipment-size chart therefore recalculates fees for each quantity using your explicit unit-price and transport assumptions. The alternate-mode line uses those same costs, not a new carrier quote. Supplier options have separate override fields; a blank override inherits the Calculator value, whereas an explicit zero stays zero. Saved scenarios remain local and full shared links expose readable financial inputs only after review.