How to Calculate US Import Duty: A Step-by-Step Guide for 2026

Step 1: Determine the Customs Value

The foundation of any duty calculation is the customs value— the price Customs and Border Protection (CBP) uses as the basis for applying tariff rates. In most cases, this is the transaction value: the price actually paid or payable for the goods when sold for export to the United States.

The customs value typically includes the cost of the goods themselves, packaging, any assists (tools, molds, or design work you provided to the manufacturer), and royalties or license fees related to the imported goods. It generally does not include international shipping or insurance costs (the US uses FOB valuation, unlike some countries that use CIF).

For example, if you buy $10,000 worth of electronics from a factory in Shenzhen and pay $500 for export packaging, your customs value is $10,500.

Step 2: Find Your HTS Code

Every product imported into the US is classified under the Harmonized Tariff Schedule (HTS), a system of numerical codes that determines the applicable duty rate. HTS codes are 10 digits long and extremely specific.

For example, a laptop computer might be classified under HTS 8471.30.0100, while a desktop computer falls under 8471.49.0000. The difference matters because duty rates can vary between codes.

You can look up HTS codes using the US International Trade Commission's HTS database. If you're unsure about your classification, a licensed customs broker can help — incorrect classification can result in penalties.

Step 3: Identify All Applicable Tariff Rates

This is where 2026 gets complicated. Your import may be subject to multiple overlapping tariff rates from different legal authorities. You need to check each one:

Base MFN Duty (Column 1 General)

Every HTS code has a base Most Favored Nation (MFN) duty rate. This is the "normal" tariff rate that applied before the recent trade actions. For many consumer goods, this rate is between 0% and 6%.

Section 122 Surcharge

The current Section 122 surcharge applies on top of the base MFN rate. As of April 2026, the baseline is 10% for most countries, with higher bilateral rates for the EU/Japan/Korea/Taiwan (15%) and India/Vietnam (18%).

Section 301 Duties (China Only)

If your goods originate in China, additional Section 301 duties apply. These range from 7.5% to 25% depending on the product category and the specific List (1 through 4B) the product falls under.

Section 232 Duties (Metals, Semiconductors, Pharma, Autos, Lumber)

Section 232 national security tariffs apply regardless of origin countryand stack on top of all other duties. As of April 2026, the covered products include: primary steel, aluminum, and copper at 50%; their derivatives at 25-50%; metal-intensive industrial/grid equipment at a transitional 15% (through Dec 2027); automobiles and parts at 25%; advanced AI semiconductors at 25% (with exemptions for US data centers and R&D); lumber at 10-50% depending on product type; and patented pharmaceuticals at up to 100% (with reduced rates for onshoring plans and select countries). Generic drugs and biosimilars are exempt. Note: products with 15% or less metal content are now exempt from metals tariffs.

Step 4: Calculate the Total Duty

The formula is straightforward:

Worked Example: Importing Steel Parts from South Korea

Step 5: Consider Your Alternatives

Once you know your duty costs, the natural next step is to explore whether sourcing from a different country would reduce your landed cost. Our tariff calculator's comparison mode lets you instantly compare the same product across 20+ origin countries.

In the steel parts example above, sourcing USMCA-compliant parts from Mexico could potentially eliminate the Section 122 surcharge entirely, reducing total duty from 38.1% to just 28.1% (MFN + Section 232).

Common Mistakes to Avoid

Using the wrong customs value.The customs value is not your retail price or the value on the commercial invoice if you've manipulated it. CBP actively audits declared values and assesses penalties for undervaluation.

Forgetting stacking tariffs.Many importers only account for one tariff rate when multiple apply. A product from China that's also made of steel could face MFN + Section 122 + Section 301 + Section 232 — four separate rates that stack on top of each other.

Assuming origin based on shipping.Country of origin is where the product was substantially transformed, not where it was loaded onto a ship. Routing Chinese goods through Vietnam doesn't make them Vietnamese.

Not updating for rate changes. Tariff rates have changed multiple times in the past 18 months and will likely change again when Section 122 expires in July 2026. Always verify current rates before making purchasing decisions.