How to Calculate Import Duty: A Practical 2026 Guide

Few numbers on a commercial invoice drive as much anxiety as the import duty figure. Underestimate it and your margin evaporates; overestimate it and you lose the sale to a competitor with tighter numbers. The good news is that import duty is not a black box. Every customs authority follows the same basic logic, and with a handful of inputs you can forecast the figure to the cent.

This guide explains exactly how import duty is calculated in 2026, from the raw inputs to the final landed cost. We will walk through two worked examples, show where traders most often go wrong, and link to the free tools you need at each step.

The anatomy of an import duty calculation

At its simplest, import duty is a percentage applied to a valuation base. The formula is:

Duty payable = Customs value × Duty rate

That apparent simplicity hides three decisions that together determine the answer: which customs value to use, which HS code classifies your product, and which duty rate applies to that code for goods of that origin. Get all three right and the arithmetic is trivial. Get one wrong and the calculation is meaningless.

Step 1: Determine the customs value

Customs value is the number your duty rate is applied to. Most jurisdictions follow the WTO Valuation Agreement, which ranks six methods in order of preference. In over 90 percent of commercial shipments the first method applies: the transaction value — the price actually paid or payable for the goods.

The dutiable transaction value usually includes:

• The invoice value of the goods (FOB price or EXW price plus inland freight to the port of export)
• International freight to the destination port or airport
• International cargo insurance
• Commissions paid to a buying agent (sometimes)
• Royalties and licence fees related to the goods (sometimes)

Countries differ in whether freight and insurance are added:

• CIF countries (most of the world, including EU, UK, Japan, Australia, Canada) — freight and insurance are included in the dutiable value.
• FOB countries (notably the United States) — duty is applied only to the FOB export price; freight and insurance are duty-free.

Understanding your destination's rule is the first step. Our tariff calculator builds the CIF value automatically; for FOB countries the freight and insurance inputs are informational only.

Worked example: building the CIF value

A UK importer buys 100 electric kettles from China:

• FOB Shenzhen price per unit: USD 14
• Total FOB value: USD 1,400
• Ocean freight Shenzhen → Felixstowe: USD 210
• Marine insurance: USD 20

CIF value = 1,400 + 210 + 20 = USD 1,630. This is the base for UK import duty.

Step 2: Classify with the correct HS code

Without an HS code there is no duty rate, and without a duty rate there is no calculation. The code is a 6-digit international classification extended to 8, 10, or even 11 digits at the national level. We have a dedicated guide to finding the right HS code and a free HS code lookup that covers common trade goods.

Electric kettles classify under HS heading 8516.71 ("electric coffee or tea makers"). For the UK import, the 10-digit commodity code is 8516 7100 00, which carries a 2.7 percent MFN duty and 20 percent VAT.

Step 3: Identify the applicable duty rate

Three families of duty rates matter in 2026:

• MFN (Most-Favoured Nation) — the default WTO rate that applies to goods from any WTO member without a preferential agreement.
• Preferential — lower rates available under Free Trade Agreements or unilateral schemes (GSP, UKGSP, EU EBA). To claim, you need a valid proof of origin.
• Trade remedies — anti-dumping, countervailing, or safeguard duties on specific HS codes from specific origins. These are often much larger than the MFN rate and can be triggered by a single declaration.

For our kettle example, China and the UK have no bilateral FTA, so the 2.7 percent MFN rate applies.

Ad valorem, specific, and compound duties

Most duty rates are ad valorem — a percentage of customs value. Some are specific — a fixed amount per unit of quantity (for example USD 0.15 per kilogram). Others are compound — the greater of a percentage or a specific amount. Always read the duty column carefully; a low-looking percentage can hide a specific component that dominates the total on low-value goods.

Step 4: Apply VAT or GST on top

In most destinations, VAT or GST is charged on CIF plus duty (and any excise). The formula is:

VAT payable = (Customs value + Duty + Excise) × VAT rate

Continuing the UK kettle example:

• CIF: GBP 1,300 (converted at 1.25 USD/GBP)
• Duty at 2.7 percent: GBP 35.10
• VAT base: GBP 1,335.10
• VAT at 20 percent: GBP 267.02
• Total duty + VAT: GBP 302.12

The same shipment into the US would calculate differently — duty is on FOB only, and there is no federal VAT, only destination state sales tax on the onward sale.

Step 5: Check for additional fees

A complete landed-cost calculation includes fees that are easy to overlook:

• US: Merchandise Processing Fee (MPF) at 0.3464 percent (min USD 32.71, max USD 634.62) and Harbor Maintenance Fee at 0.125 percent for sea freight.
• EU: none beyond duty and VAT at a federal level, but member states may charge port dues.
• UK: Customs declaration fees charged by the broker (not by HMRC).
• Many countries: anti-dumping, countervailing, and section-specific duties (for example Section 301 in the US).

Using the free duty calculator

Our tariff calculator takes goods value, freight, insurance, HS code, origin, and destination, then returns the duty rate, duty amount, VAT, and total landed cost in real time. Run three scenarios to stress-test your margin:

1. Your target buy price, current freight, current insurance.
2. A 20 percent freight increase (ocean volatility is common in 2026).
3. A change of origin to a non-FTA country — useful when your supplier moves factories.

If any scenario breaks the margin, you have a risk to plan for before the order is placed.

Common calculation mistakes

Mistake 1: Using retail price instead of transaction value. Customs does not care what you will sell the kettle for; only what you paid for it.

Mistake 2: Forgetting currency conversion. Every customs authority publishes a monthly exchange rate. Using the commercial spot rate will cause small but recurring differences.

Mistake 3: Treating VAT as a cost. For VAT-registered importers, import VAT is reclaimable. It affects cash flow but not the bottom line.

Mistake 4: Ignoring de minimis on small shipments. Sample shipments under the threshold can be informal and duty-free; stack them onto one commercial entry and you lose the exemption.

From calculation to quote

Once you are comfortable with the arithmetic, the next job is turning the numbers into a reliable quote. We recommend keeping a spreadsheet with three columns: supplier cost, landed cost (using our calculator), and target sell price. Re-run the calculator every time you re-order, because tariff rates, exchange rates, and freight rates all move. The 2026 shipping cost guide will help you nail down the freight side.