Tariff Calculator: How to Calculate Import Duties Step by Step

To calculate import duties, you need three things: the HS/HTS code of your product, the country of origin, and the customs value. With these three inputs you can determine exactly how much you'll owe US Customs and Border Protection (CBP) before your goods arrive. Getting this calculation wrong can mean unexpected costs that destroy your profit margins — or worse, penalties for underpayment. This guide walks you through the complete formula with real numbers.

The Duty Calculation Formula

The core formula is straightforward: Total Import Costs = (Customs Value × Duty Rate) + Merchandise Processing Fee + Harbor Maintenance Fee + any additional duties. Let's break down each component.

Step 1: Determine Your HTS Code

Every product imported into the US is assigned a Harmonized Tariff Schedule (HTS) code — a 10-digit number that determines your duty rate. The first 6 digits are internationally harmonized (the HS code), while digits 7-10 are US-specific. For example, men's cotton t-shirts fall under HTS 6109.10.0012 with a duty rate of 16.5%. Getting the wrong code could mean paying 0% when you should be paying 32%, and that's a compliance violation.

Step 2: Determine the Customs Value

The customs value is the base on which duties are calculated. For most imports, this is the transaction value — the price you actually paid or will pay for the goods, including: the purchase price of the goods, packing costs incurred by the buyer, any selling commission, the value of any assist (materials or tooling you provided to the manufacturer), and any royalty or license fee you're required to pay as a condition of sale. International freight and insurance to the US port are NOT included in the US customs value (unlike many other countries that use CIF value).

Step 3: Apply the Duty Rate

Multiply your customs value by the applicable duty rate from the HTS. The rate depends on the country of origin: Column 1 General (MFN) rates apply to most countries. Column 1 Special rates apply under trade agreements like USMCA, CAFTA-DR, or programs like GSP. Column 2 rates (significantly higher) apply to a few countries like Cuba and North Korea.

Step 4: Add Merchandise Processing Fee (MPF)

The MPF is charged on all formal entries (shipments valued over $2,500). The rate is 0.3464% of the customs value, with a minimum of $31.67 and a maximum of $614.35 per entry in 2026. For our ceramic mugs example: $25,000 × 0.3464% = $86.60.

Step 5: Add Harbor Maintenance Fee (HMF)

The HMF applies only to ocean shipments and is 0.125% of the customs value. There's no cap. For our example: $25,000 × 0.125% = $31.25. Air shipments are exempt from HMF.

Step 6: Check for Additional Duties

Several programs can add duties on top of the base MFN rate:

• Section 301 tariffs — Additional 7.5% to 100% on Chinese goods depending on the product category. As of 2026: 100% on EVs, 50% on semiconductors and solar cells, 25% on steel/aluminum/batteries/critical minerals, 25% on most other covered goods.
• Section 232 tariffs — 25% on steel, 10% on aluminum from most countries (separate from Section 301).
• Antidumping duties (AD) — Can range from 5% to over 500%. Check the ITC's AD/CVD database for active orders.
• Countervailing duties (CVD) — Offset foreign government subsidies. Often paired with AD duties.

Complete Calculation Example

Let's calculate the total import costs for a real scenario. You're importing $100,000 worth of lithium-ion batteries (HTS 8507.60.0020) from China via ocean freight.

1. Customs value: $100,000
2. MFN duty rate: 3.4% → $3,400
3. Section 301 tariff (List 3): 25% → $25,000
4. MPF: 0.3464% → $346.40 (within min/max)
5. HMF: 0.125% → $125.00
6. Total import costs: $28,871.40
7. Effective duty rate: 28.87%

Ways to Reduce Import Duties

• Trade agreements — If your goods qualify under USMCA, CAFTA-DR, or other FTAs, duty rates may be 0%.
• Foreign Trade Zones (FTZ) — Defer, reduce, or eliminate duties by storing or manufacturing in an FTZ.
• Tariff engineering — Legal product modifications to qualify for a lower-duty classification.
• Duty drawback — Recover up to 99% of duties paid on imported goods that are subsequently exported.
• First Sale valuation — Use the price from the first sale in a multi-tiered transaction to reduce customs value.

Calculate Your Duties Instantly with Camtom

Manually calculating duties for every product is tedious and error-prone. Camtom's AI-powered platform automatically classifies your products, identifies the correct HTS code, calculates all applicable duties and fees — including Section 301, 232, and AD/CVD — and estimates your total landed cost in seconds. Try the free duty calculator at camtomx.com/aranceles or start a free trial to classify products with AI.