How to Calculate Import Duty on a US Shipment

US import duty is calculated by multiplying your goods' customs value by the duty rates that apply to their HTS code and country of origin, then adding any Chapter 99 layers like Section 301 or Section 232, and finally the Merchandise Processing Fee and, for ocean freight, the Harbor Maintenance Fee. That's the whole formula. The hard part is getting each input right.

Here's the process in eight steps, in the order a broker works through it, current as of October 2026 — plus one fully worked example you can copy into a spreadsheet.

Duty is usually the second-biggest cost in a landed-cost model after the goods themselves, and in 2026 it has moved more than in any year in recent memory. A product that cost 6% to bring in three years ago can now carry a stack of 18% or more once a Section 301 layer is added. If your pricing still runs on a single "duty %" column, it's almost certainly wrong for some SKUs.

The law also puts the work on you. The importer of record has to use "reasonable care" in declaring value, classification and origin (Cornell LII). Knowing how the number is built is how you catch errors before CBP does — and how you spot overpayments you can still get back.

Every calculation starts with the product's 10-digit code in the Harmonized Tariff Schedule of the United States, because the code sets the base duty rate and decides which extra tariffs apply. The schedule is published by the US International Trade Commission (USITC). The first eight digits set the rate; the last two are a statistical suffix.

Classification follows the General Rules of Interpretation, applied in order, and turns on what the product is, what it's made of and what it does — not its marketing name. If you're unsure, search CBP's past rulings in CBP CROSS or request a binding ruling under 19 CFR Part 177 (eCFR). Our guide to finding the right HTS code walks through it.

For most imports, the customs value is the transaction value: the price actually paid or payable for the goods when sold for export to the United States, plus a short list of required additions (19 U.S.C. § 1401a). It's usually your commercial invoice price.

What's excluded. Unlike the EU, Canada and most other countries, the US values imports on a roughly FOB basis. International freight and insurance are left out of dutiable value when they're separately identified (19 CFR 152.103). So if you buy on CIF or DDP terms, back out the international freight and insurance — don't pay duty on them.

What must be added if it isn't already in the price (19 CFR 152.103):

Assists are the one most often missed. If you shipped a $20,000 mold to your supplier, part of that value belongs in your entered value.

Country of origin is where the goods were made or last substantially transformed — not where they shipped from — and it decides which rate column and which extra tariffs apply. Goods made in Vietnam but shipped through Singapore are still Vietnamese for duty purposes. Assembly or processing in a third country only changes origin if it creates a new article with a different name, character or use. Origin also drives Section 301 and AD/CVD exposure, so it's the input that most often moves the final number.

The base duty is the "General" rate in column 1 of the HTSUS for your 8-digit line, which applies to goods from every country with normal trade relations (USITC). Most rates are ad valorem (a percentage of value), but some are specific (cents per kilo or per unit) or compound (both). Base duty = customs value × general rate. Goods from Cuba and North Korea pay the much higher column 2 rates; Russia and Belarus lost normal trade relations in 2022 and also pay column 2.

Additional tariffs show up on your entry as separate Chapter 99 lines (9903 numbers) stacked on top of your product's regular code, and each one is calculated on the same customs value. As of October 2026, the main layers are:

Two layers are gone. CBP stopped collecting IEEPA tariffs on February 24, 2026 (Thompson Hine), after the Supreme Court held on February 20 that IEEPA didn't authorize them; duties already paid are being refunded through CBP's CAPE process (CBP). The 10% Section 122 surcharge that followed ran from February 24 to July 24, 2026 (Z2Data). Neither belongs in a calculation for goods entered today.

If your goods qualify under a free trade agreement, the FTA's "Special" rate replaces the general rate — often with zero duty — but only if you claim it on the entry and can back it up. Qualifying is about rules of origin, not just where the goods were shipped from, and you need the supporting records on file. Preference doesn't automatically wipe out the Chapter 99 layers: USMCA-qualifying goods are exempt from the new country-level Section 301 duties, but each layer has its own exemption rules, so check them one by one.

The Merchandise Processing Fee is 0.3464% of the entered value of a formal entry, with a per-entry minimum of $34.58 and maximum of $670.86 for fiscal year 2027, which began October 1, 2026 (Federal Register). In practice the minimum kicks in below about $9,983 of value, and the cap is reached at about $193,666. The 0.3464% rate itself didn't change; only the floor and ceiling moved (CBP CSMS #70086122).

The Harbor Maintenance Fee is 0.125% of the value of cargo unloaded at US ocean ports, with no cap (26 U.S.C. § 4461). Air and truck shipments don't pay it.

Antidumping and countervailing duties apply only when a product falls within the scope of a Commerce Department order for a specific country, and when they apply they're often the biggest number on the entry. They're paid as cash deposits at entry, at rates that can vary by producer, and the final amount can be adjusted years later in an administrative review (International Trade Administration). If your product is anywhere near an active case, get scope confirmed before you import at volume.

Add it all up and you have your duty bill. Here's what that looks like on a real-sized shipment.

Two things to notice. The Section 301 layer is more than double the base duty, so origin matters more than classification here. And if the same goods came by air, HMF would drop off and the total would be $9,423.20.

The formula hasn't changed in decades: value times rate, plus fees. What's changed is how many rates there are and how often they move. In 2026 alone, one layer was struck down, a replacement came and went, and a new country-level Section 301 layer took its place. Importers who keep value, classification and origin clean — and model each layer separately — can reprice in an afternoon when the next change lands.

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