Once you know your product's HTS code and its duty rate, calculating what you'll owe at customs is straightforward. But duty rates come in several forms — and each is calculated differently. Here's how to work it out.
The Three Types of Duty Rates
1. Ad Valorem Rates (Most Common)
An ad valorem rate is a percentage of the product's customs value. This is the most common format — for example, 5% or 12.5%.
Formula: Duty = Transaction Value × Rate
Example: You import $10,000 worth of furniture with a 5.3% duty rate. Duty = $10,000 × 0.053 = $530
2. Specific Rates
A specific rate is a fixed amount per unit of weight or quantity — for example, $0.05/kg or ¢1.5/liter.
Formula: Duty = Unit Rate × Quantity
Example: You import 500 kg of a product with a rate of ¢2.2/kg. Duty = 500 × $0.022 = $11
3. Compound Rates
Some products have compound rates that combine both an ad valorem and a specific component. For example: "6.5% + $1.25/kg"
Formula: Duty = (Transaction Value × Ad Valorem %) + (Weight × Specific Rate)
What Is "Transaction Value"?
For customs purposes, the transaction value is generally the price actually paid or payable for the goods when sold for export to the United States. This typically means the invoice price, not including freight and insurance (though customs can require CIF value in some cases). Always check with your customs broker if you're unsure.
What Else Might You Owe?
Customs duty is just one component of the total cost of importing. Depending on your shipment, you may also owe:
- Merchandise Processing Fee (MPF): 0.3464% of the entered value (min $32.71, max $634.62 per entry)
- Harbor Maintenance Fee (HMF): 0.125% of the value (for ocean shipments)
- Section 301 tariffs: Additional tariffs on goods from China
- Anti-dumping / countervailing duties: For certain products from specific countries
A licensed customs broker can provide a full landed cost estimate for your specific shipment.
Important Disclaimer
The duty calculator on LookupHTS is for estimation purposes only. Actual duty owed depends on many factors including valuation method, country of origin, FTA eligibility, and any applicable additional tariffs. Always verify with CBP or a licensed customs broker before filing.
Understanding Customs Valuation
The accuracy of your duty calculation depends entirely on the accuracy of your customs value. The United States follows the World Trade Organization (WTO) Customs Valuation Agreement, which establishes a hierarchy of six valuation methods. The primary method — and the one used in the vast majority of imports — is transaction value, which is the price actually paid or payable for the goods when sold for export to the United States.
Transaction value includes more than just the invoice price. It also includes any assists (materials or tools provided to the manufacturer at no charge), royalties or license fees paid as a condition of sale, and the value of any packing costs. Conversely, certain costs can be excluded from transaction value if they are separately identified on the invoice, including international freight, marine insurance, and U.S. inland freight. Getting the valuation right is essential because even a small error in declared value gets multiplied by the duty rate across every entry.
Landed Cost: The Full Picture
Importers who focus only on the customs duty often underestimate their true landed cost. A complete landed cost calculation includes the product purchase price, international freight and insurance, customs duties (general rate plus any additional tariffs), the Merchandise Processing Fee, the Harbor Maintenance Fee for ocean shipments, any anti-dumping or countervailing duties, domestic transportation from port to warehouse, customs broker fees, and any required inspections or certifications. For products subject to Section 301 tariffs, the additional duty alone can be 7.5% to 25% on top of the base rate, significantly changing the economics of your sourcing decision.
Tips for Reducing Duty Costs Legally
There are several legitimate strategies to reduce your duty burden. First, verify whether your product qualifies for any FTA or preferential trade program — many importers pay full duty on goods that could enter at a reduced or zero rate. Second, consider whether your product could be classified under a different but equally valid HTS code with a lower rate; some products genuinely fall on the boundary between two codes, and the classification with better support may also carry a lower duty. Third, explore Foreign Trade Zones (FTZs), which allow you to defer, reduce, or eliminate customs duties on imported goods that are stored, assembled, or manufactured within the zone. Finally, for recurring imports, consider filing for a binding ruling from CBP to lock in a favorable classification and protect yourself from future disputes.