Carat is the first thing most calculators get wrong
Zakat is owed on gold, not on the copper and silver that gold is mixed with to make it hard enough to wear. Carat measures that in twenty-fourths: 24 carat is pure, 22 carat is 91.67% gold, 21 carat is 87.5%, 18 carat is three quarters.
A jewellery box of 22-carat bangles and 18-carat rings is therefore not one weight. A 40-gram bangle at 22 carat holds 36.67 grams of gold; the same 40 grams at 18 carat holds 30. Enter each piece as it sits on the scale and the carat takes the alloy back out — which is why this page asks piece by piece rather than for a single total.
The question the schools answer differently
Whether a woman owes zakat on the jewellery she actually wears is one of the oldest live differences in the subject, and in many households it decides most of the answer.
The Hanafi position is that gold and silver are wealth by their nature, so what they are used for does not change their standing: all of it is zakatable. The Maliki, Shafi’i and Hanbali positions exempt jewellery worn lawfully and in normal quantity, treating it as something in use rather than wealth being stored — much as a house is not zakatable however valuable it is.
The exemption is about use, and only about use. Coins, bars, investment gold and jewellery kept in a safe are zakatable on every view, with no exception. This page marks each piece accordingly and tells you what the other position would have produced, because a reader deciding between two schools deserves both numbers rather than one presented as the answer.
The threshold is measured on everything
The nisab — 87.48 grams of gold or 612.36 grams of silver — is not measured against the jewellery on its own. It is measured against everything zakatable that you hold: the metal, your cash, your bank balances, your investments, your business stock. A jewellery box below the threshold on its own can still be zakatable once your savings sit beside it.
That is why there is a field above for your other wealth, and why this page ends by pointing at the full zakat calculator rather than claiming to be one. It also does not ask about the lunar year, which the full calculator does — zakat falls due once your wealth has stood above the nisab for a complete hawl.