Any import duty calculator is doing the same three steps, and knowing them is more useful than any particular calculator, because the inputs are what people get wrong rather than the arithmetic. Duty is charged on the customs value, which is the price paid plus shipping and insurance. The rate comes from the commodity code and the country of origin. Import VAT is then charged on that whole total including the duty, and the carrier adds a handling fee of its own that no calculator knows about.
The three inputs a calculator needs from you
The commodity code, the country of origin and the customs value. The code is the one people get wrong: it is specific to what the item is made of and what it is for, not to what it is called, and it is your responsibility even when a supplier printed it on the invoice. Origin is where the goods were made rather than where they were shipped from, which matters when a European warehouse sends goods manufactured elsewhere.
Why the answer is often lower than expected and the bill higher
Duty is zero on a great many goods, so the duty line of a calculation frequently comes out at nothing. What still arrives is import VAT on goods plus shipping, and the carrier's handling fee for clearing the entry and collecting the money. That fee is a fixed amount, published by nobody in advance, and on a low-value parcel it is routinely the largest single component of what the recipient is asked for.
Use GOV.UK for the rates, not a carrier's page
Thresholds and rates change, and a commercial page summarising them ages badly. GOV.UK publishes the current position and the trade tariff is where a commodity code is looked up properly. This record deliberately does not restate a threshold: a figure quoted here would be right on the day it was written and wrong later, which is precisely the failure mode a dated record exists to avoid.
Questions people ask about uk import duty calculator
How is UK import duty calculated?
On the customs value, which is the price paid plus shipping and insurance, at a rate set by the commodity code and the country of origin. Import VAT is then charged on that total including the duty.
What are UK customs charges on a parcel?
Duty where it applies, import VAT on goods plus shipping plus duty, and the carrier's own handling fee for clearing the entry, which nobody publishes in advance.
Why do I owe VAT when the duty is zero?
They are separate charges. Duty is zero on many goods; import VAT still applies to the total value including shipping.
Where do I find the right commodity code?
The UK trade tariff on GOV.UK. The code depends on what the item is made of and what it is for, not on what it is called, and it is your responsibility even if a supplier supplied it.