How to Calculate US Import Duty: Step-by-Step Guide
Founder, USTariffCalc.com · LinkedIn
US import duties are calculated on customs value — the product cost plus freight and insurance paid to bring goods to the US port of entry. That base is then multiplied by up to four separate tariff rates, depending on the product and country of origin. This is the step-by-step formula.
1. The Formula
Here's the complete formula for calculating your total import cost in 2026:
+ (Customs Value × MFN Rate)
+ (Customs Value × Section 122 Rate)
+ (Customs Value × Section 301 Rate)*
+ (Customs Value × Section 232 Rate)*
+ Merchandise Processing Fee
+ Harbor Maintenance Fee
* If applicable based on country/product
2. Step-by-Step Calculation
Determine Your Customs Value
Your customs value is the transaction value of the goods plus shipping and insurance costs to the US port of entry. This is the base amount that all duty percentages are applied to.
Customs Value = Product Cost + Freight + Insurance
Find Your MFN Base Rate
Every product imported into the US has a Harmonized Tariff Schedule (HTS) code. This 10-digit code determines your MFN (Most Favored Nation) base duty rate. You can look up HTS codes at the US International Trade Commission website (hts.usitc.gov).
MFN rates range from 0% on many raw materials and electronics up to 48% on certain footwear and apparel.
Check Section 122 Applicability
As of April 2026, a 10% Section 122 surcharge applies to imports from most countries. Two key exemptions exist: USMCA-qualifying goods from Canada and Mexico, and products covered by Section 232 tariffs (steel, aluminum, autos, semiconductors). If neither exemption applies, add 10%.
May 2026 legal update: The Court of International Trade ruled Proclamation 11012 invalid. An appeal is pending; a CAFC stay keeps tariffs in force. Preserve all import records (Feb 24 – Jul 24, 2026) in case refunds become available. Read the full ruling analysis →
Check Section 301 (China Only)
If your goods originate in China, Section 301 tariffs apply at rates ranging from 7.5% to 100% depending on the product category. Check the USTR website for the current list of covered products and their rates.
Check Section 232 (Sector-Specific)
If your product falls into one of the covered sectors — steel (50%), aluminum (50%), automobiles (25%), auto parts (25%), semiconductors (25%), or copper (25%) — Section 232 rates apply regardless of country of origin. Remember: Section 232 products are exempt from Section 122.
Add Processing Fees
Merchandise Processing Fee (MPF): 0.3464% of customs value, with a minimum of $31.67 and a maximum of $614.35 per entry.
Harbor Maintenance Fee (HMF): 0.125% of customs value for ocean shipments.
3. Complete Example
Scenario: Importing Furniture from Vietnam
Product: Wooden furniture
Customs Value: $25,000 (product $22,000 + shipping $3,000)
Country: Vietnam (not USMCA, not China)
Product: Not a Section 232 sector
Section 122 (10%): $25,000 × 0.10 = $2,500
Section 301: $0 (not China)
Section 232: $0 (not covered sector)
MPF: $25,000 × 0.003464 = $86.60
HMF: $25,000 × 0.00125 = $31.25
Total duties & fees: $3,367.85
Total landed cost: $28,367.85
Effective rate: 13.5%
4. Common Mistakes to Avoid
Using the wrong customs value. Duties are calculated on the total value including freight and insurance, not just the product price. Undervaluing goods is a customs violation with serious penalties.
Forgetting that tariffs stack. Many importers calculate only one tariff layer and are shocked when CBP assesses multiple layers. MFN, Section 122, Section 301, and Section 232 all add to each other.
Assuming USMCA exemption without qualifying. Just because goods ship from Canada or Mexico doesn't mean they qualify for USMCA treatment. Products must meet specific rules of origin — if components are sourced from outside North America, the finished product may not qualify.
Missing Section 232 exemptions from Section 122. If your product is covered by Section 232, you should not be paying the 10% Section 122 surcharge on top of it. This is money left on the table if your customs broker doesn't catch it.
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