Quick answer
Duty estimate = customs value × applicable duty rate.
The difficult part is not the multiplication. The difficult part is confirming the correct classification, origin treatment, rate and customs value for the destination country.
ImportMetric does not determine your legal tariff classification or official duty rate.
What you need
Four inputs matter before the formula.
Product classification
The HS, HTS, CN or other destination-specific tariff classification determines which tariff line and rules may apply.
Country of origin
Origin can affect ordinary tariff rates, trade-agreement preferences, anti-dumping measures and other treatment.
Destination market
The importing country or customs territory determines which tariff schedule and valuation rules to use.
Customs value / duty base
The valuation basis may include more than invoice value. Freight, insurance, assists, royalties or other adjustments can matter under local rules.
Worked example
A transparent planning estimate.
Assume product value of $8,400, international freight of $620, insurance of $65 and a verified planning duty rate of 6.5%.
This matches the simplified basis used in ImportMetric's current duty-planning tools. It is a disclosed assumption, not a claim that every customs authority uses the same base.
Finding the rate
Use official tariff sources for the destination country.
Search using the product classification and origin, then review any preferential rate, additional duty or product-specific measure. When the classification is uncertain or the financial exposure is material, a customs broker or qualified specialist can help verify it.
A rate that is correct for one destination, material composition or use case may be wrong for another.
Customs value
Know what the percentage is applied to.
A 6.5% rate on $8,400 and a 6.5% rate on $9,085 produce different duty. This is why the duty base should be documented beside the rate rather than hidden inside a single estimate.
Also keep import VAT/GST or sales tax separate from customs duty when the destination rules treat them differently.
Common mistakes