US Customs Duty Calculator: How Import Duty Is Calculated and How to Estimate It

By SaveOnShip Editorial Team — Logistics Data Editorial Team. Last updated: 2026-08-28.

<div class="quick-answer"> <strong>Quick answer:</strong> US import duty is calculated by multiplying the <strong>customs value</strong> of your goods (usually the FOB price you paid) by the <strong>HTS duty rate</strong> for your product's classification. On top of that duty, most entries also pay the <strong>Merchandise Processing Fee (MPF)</strong> and, for ocean freight, the <strong>Harbor Maintenance Fee (HMF)</strong>, plus any additional tariffs such as Section 301 duties on Chinese goods. A US customs duty calculator runs this formula for you — but it returns an <strong>estimate</strong>, not a bill, because the final amount is set by US Customs and Border Protection based on your exact HTS code and declared value. </div>

TL;DR: A US customs duty calculator is only as good as the two numbers you feed it — the right HTS code and the correct customs value. Get those and the formula is simple arithmetic: duty = customs value × duty rate, plus MPF, HMF, and any extra tariffs. This guide walks the three steps, works a real China-to-USA example, and explains why every calculator gives an estimate rather than the exact amount CBP will charge.

Import duty is one line of your landed cost — the freight side is covered in our <a href="/blog/landed-cost-calculator">landed cost calculator guide</a>, and the classification that drives your duty rate in our <a href="/blog/harmonized-tariff-code">harmonized tariff code guide</a>.

How is US import duty actually calculated? (the formula)

The core formula is straightforward:

Import duty = customs value × HTS duty rate

What makes it feel complicated is that each input takes work. The "customs value" is usually the price you paid for the goods (the FOB value), not the retail price. The "duty rate" comes from your product's HTS classification, and rates vary from 0% to over 30% depending on the product. Then the total you actually pay stacks additional fees on top of the duty itself.

A US customs duty calculator automates this: you enter the product, its value, and origin, and it applies the duty rate and fees. But the calculator is doing the same arithmetic you can do by hand once you have the right HTS code and value — which is why the next two steps matter more than the tool.

Step 1: find the right HTS code and duty rate

Every product imported into the US is classified under a ten-digit HTS (Harmonized Tariff Schedule) code, and each code carries a duty rate. The duty rate lives in the HTS itself, published by the US International Trade Commission. The official source is the <a href="https://www.usitc.gov">USITC</a> HTS search, and the import-side rules are on <a href="https://www.cbp.gov/trade/programs-administration/determining-duty-rates">U.S. Customs and Border Protection's determining duty rates page</a>.

This is the step where most estimates go wrong. The same product can fall under several plausible codes with different rates, and misclassification either overpays duty or triggers penalties. For a worked walkthrough of how codes are structured, see our <a href="/blog/harmonized-tariff-code">harmonized tariff code guide</a>. The duty rate you find here — say 3.2% or 25% — is the single biggest driver of your estimate.

Step 2: determine the customs value of your goods

US import duty is generally assessed on the transaction value — the price actually paid for the goods, roughly the FOB value. That means duty is calculated on what you paid your supplier, not on your selling price and usually not including international freight and insurance (the US is a FOB-valuation country, unlike CIF-valuation countries).

So a $10,000 purchase of goods is dutiable at $10,000 even if you paid $2,000 for freight. Getting the customs value right matters as much as the rate: undervaluing goods to cut duty is customs fraud, and overvaluing overpays. This is why a calculator's output is only as reliable as the value you enter.

Step 3: add MPF, HMF, and any extra tariffs

The headline duty is rarely the whole bill. Most commercial entries add:

• Merchandise Processing Fee (MPF) — an ad valorem fee on formal entries, roughly 0.3464% of value, subject to minimum and maximum caps per entry.
• Harbor Maintenance Fee (HMF) — about 0.125% of value, charged only on ocean shipments.
• Additional tariffs — Section 301 duties on many Chinese-origin goods, and other trade-remedy or product-specific tariffs, which can add 7.5%–25% or more on top of the base HTS rate.

These percentages are approximate reference figures that change over time — always confirm the current rate with CBP or your customs broker before relying on a number. The point is that your total import cost is the duty rate plus these stacked fees, so the headline HTS rate understates what you will actually pay.

A worked example: import duty on a China-to-USA shipment

A quick case study. A cross-border seller imports $20,000 of consumer goods from China by sea, classified under an HTS code with a 5% base duty rate, and the goods are also subject to a 25% Section 301 tariff.

• Base duty: $20,000 × 5% = $1,000
• Section 301 tariff: $20,000 × 25% = $5,000
• MPF (approx. 0.3464%): ≈ $69
• HMF (approx. 0.125%): ≈ $25

Estimated total import charges ≈ $6,094 — on a $20,000 shipment, the stacked tariffs and fees come to roughly 30% of the goods' value, not the 5% the headline HTS rate suggested. This is why the duty rate alone is misleading, and why the seller should run the full calculation before pricing the product. These figures are an approximate reference band for orientation; the exact duty, fees, and any applicable tariffs for a specific shipment require manual confirmation with CBP or a licensed customs broker.

Why a US customs duty calculator gives an estimate, not a bill

No calculator can tell you exactly what US customs will charge, for three reasons. First, the final classification is made by CBP, and a calculator can only apply the HTS code you chose — pick the wrong code and the estimate is wrong. Second, the dutiable value can be adjusted by CBP. Third, tariffs and fee rates change, and a calculator may not reflect the current Section 301 or fee schedule.

So treat every calculator result as an estimate for planning and pricing, not a bill. The exact amount is determined at entry by CBP. This is also why duty is only one line of landed cost — the freight, insurance, and destination charges around it all require manual confirmation, and public figures are approximate reference bands.

SaveOnShip is a China-to-global logistics route lookup and comparison platform — not a carrier, freight forwarder, customs broker, or booking service. You can use it to compare <a href="/companies">Chinese logistics companies</a> by route coverage, price band, and data freshness, browse <a href="/countries">destination-country route options</a>, review <a href="/best">top-rated providers by route</a>, and read <a href="/data-information">how our route data is sourced and bounded</a> before you estimate duty and arrange freight. For authoritative duty rates and import rules, <a href="https://www.cbp.gov">U.S. Customs and Border Protection</a> and the <a href="https://www.usitc.gov">USITC</a> are the official references.

Frequently asked questions

How do I calculate customs duty?

Multiply the customs value of your goods (usually the price you paid, FOB) by the HTS duty rate for your product's classification. Then add the Merchandise Processing Fee, the Harbor Maintenance Fee if shipping by sea, and any additional tariffs such as Section 301 duties. The result is your estimated total import charge.

How much will US customs charge me?

It depends on your product's HTS code, its customs value, and any applicable tariffs. Duty rates range from 0% to over 30%, and additional tariffs and fees can push the total well above the base rate. A calculator gives an estimate; the exact amount is set by CBP at entry, so confirm with CBP or a customs broker.

How much can you bring into the U.S. without duty?

For returning travelers there is a personal exemption (commonly $800). For commercial imports, there is no general duty-free allowance — duty applies based on the HTS classification and value, and de minimis rules for low-value shipments have been changing, so confirm the current threshold with CBP.

Is a US customs duty calculator result what I actually pay?

No — it is an estimate. The calculator applies the HTS code and value you enter, but CBP makes the final classification and valuation at entry, and tariff and fee rates change. Use the result for planning and pricing, and confirm the exact amount with CBP or your customs broker.

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> Disclaimer: SaveOnShip is a logistics route lookup and comparison platform — not a freight forwarder, carrier, customs broker, insurer, or booking service. Duty rates, fees, tariff percentages, and all figures in this article are approximate references compiled from public sources for orientation only; they are not tax, legal, or customs advice, and not a binding calculation. Actual duty, fees, and tariffs are determined by US Customs and Border Protection at entry and require manual confirmation with CBP or a licensed customs broker. Tariff schedules and de minimis rules change — verify current rates before relying on any estimate.

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