How Is a U.S. Import Tariff Calculated in 2026?

The formula

Every layer of U.S. import duty is an ad valorem percentage applied to the same customs value. The layers are added to each other; no layer is applied on top of another layer.

Total duty = Customs value × (MFN rate + Section 301 rate + Section 232 rate + …)
Fees       = MPF (0.3464% of value, min $33.58 / max $651.50) + HMF (0.125%, ocean only)
Owed to CBP = Total duty + Fees

Three things follow from this:

• Rates add, they do not multiply. 16.5% + 7.5% + 12.5% is a 36.5% duty, not 1.165 × 1.075 × 1.125 (= 40.9%).
• Freight is not in the base. Unlike the EU or Canada, which value goods CIF, the United States uses a transaction value that excludes international freight and insurance when they are shown separately.
• Fees are not duties. The Merchandise Processing Fee (MPF) and Harbor Maintenance Fee (HMF) are user fees under a different statute; they are charged per entry and are not refundable under trade programs that refund duties.

What "customs value" means

U.S. customs value is the transaction value defined in 19 U.S.C. § 1401a: the price actually paid or payable for the goods when sold for export to the United States, plus certain additions if they are not already in the price:

In practice, for most e-commerce and wholesale shipments the customs value is the FOB / EXW invoice price of the goods. If you quote DDP, you still declare the goods value — not the DDP price — and the duty you pay is your cost.

The layers, and where each one comes from

A single HTS code can hit several tariff programs at once. Each layer has its own statute, its own Federal Register notice and its own effective date; our calculator lists them separately so every number is traceable.

Two programs you may still see referenced no longer apply to new entries: the IEEPA "reciprocal" and fentanyl tariffs (Chapter 99 headings 9903.01 / 9903.02) ended on 2026-02-24 after the Supreme Court ruling, and duties paid under them between 2025-02-04 and 2026-02-24 are refundable through the CBP CAPE process — see our IEEPA refund guide. The de minimis duty-free threshold for shipments under $800 has been suspended for all countries since 2025-08-29, so low-value parcels now pay the same duty stack.

Specific and compound rates

Not every MFN rate is a percentage. The HTSUS also uses:

• Specific rates — an amount per unit of quantity, e.g. rice at 2.1¢/kg. You need the net weight (or count) of the entry, not the value.
• Compound rates — a percentage plus a specific rate, e.g. steel screws and bolts at 9% + 0.5¢/kg.

Section 301 and Section 232 layers are still ad valorem on the customs value even when the MFN base is specific. Our calculator shows the ad valorem layers and asks for weight where a specific component applies; if weight is missing, the result is labeled a partial estimate.

Worked example: cotton T-shirts from China

Take HTS 6109.10.00 (knitted cotton T-shirts), $10,000 of goods on a formal ocean entry from China, 1,000 units. The table below is generated live from the same ruleset the calculator uses, so it always matches what the tool returns:

Read it from the top: the MFN rate, the China Section 301 rate and the global Section 301 tier are each multiplied by the same $10,000 and added. MPF and HMF are then charged on that same $10,000 — not on the value plus duty. Divide the total by the unit count and you have the per-unit duty to build into your landed cost.

Change any one input — origin country, HTS code, entry date, or ocean vs air — and the stack changes. That is why a "tariff on China" is not a single number: it is the sum of whichever layers the specific code triggers on the specific date.

Effective tariff rate vs. statutory rate

The statutory rate is what a single program says: "25% under Section 301." The effective tariff rate on a shipment is everything you actually paid divided by the customs value:

Effective rate = (all duties + fees) ÷ customs value

In the example above the effective rate is roughly 37% even though no single program charges 37%. This is the number to use when you compare suppliers in different countries or decide whether to pass cost through in your price. (Economists also use "effective tariff rate" for the average across all U.S. imports; that macro figure is not what applies to your entry.)

What changes the answer

• Entry date. Rates are time-bound. The global Section 301 program started 2026-07-24; FY2027 MPF minimum and maximum change on 2026-10-01; Section 232 pharmaceutical tariffs begin 2026-09-29. Our engine keys every rate to its effective window, and the Tariff Radar logs each change with its Federal Register source.
• Country of origin — where the goods were made or last substantially transformed, not where they shipped from. Transshipping through a third country does not change origin.
• Entry type. Formal entries pay ad valorem MPF; postal informal entries (≤ $2,500) pay a flat fee instead. HMF applies only to goods arriving by vessel.
• AD/CVD orders on the product-country pair, which sit on top of everything above.
• Preferential programs such as USMCA can reduce the MFN layer to zero for qualifying goods; they generally do not remove Section 232 or 301 layers.

The fastest way to see your own stack is to enter the HTS code and origin in the U.S. tariff calculator — each row links to the notice that created it.