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18K Gold Purity

What 18K gold means: 75.00% gold, stamped 750, with the pure gold weight per tola and per troy ounce.

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In short 18K gold is 18 parts gold in 24, which works out to 750.00 parts per thousand and 75.00% gold by weight; the remaining 25.00% is alloy, usually copper, silver, zinc or nickel, and it is what sets the colour and the hardness. It is stamped 750. Here the arithmetic lands exactly on the mark, so 750 needs no rounding at all. In practical weights, one tola of 18K — 11.6638 grams gross — contains 8.748 grams of pure gold, and one troy ounce of it contains 23.328 grams; gold is priced per troy ounce of 31.1035 grams, never per the 28.35 gram ounce on a kitchen scale. This is the standard in Italy, Switzerland, France, luxury brands worldwide, where it is used for fine and branded jewellery, watch cases. One thing to keep straight: karat is a ratio out of 24 and says nothing whatever about weight, while the carat that gemstones are sold in is a mass unit of exactly 0.2 grams. A two carat stone weighs 0.4 grams; a 18 karat piece can weigh anything at all.

How to use the 18K Gold Purity

  1. Read the fineness and percentage for 18K.
  2. Check the pure gold weight per tola and per troy ounce.
  3. Switch the selector to compare with another karat.

About the 18K Gold Purity

What 18K gold means in fineness, percentage and pure gold weight, and where it is the standard.

What people use it for

  • Reading a 750 hallmark and knowing what it guarantees.
  • Working out the gold content of a 18K piece.
  • Comparing 18K against the other standards before buying.

Details

Fineness750.00 parts per thousand
Gold content75.00% by weight
Hallmark750
Pure gold per tola8.748 g of 11.664 g
Standard inItaly, Switzerland, France, luxury brands worldwide
PrivacyEverything runs in your browser. Nothing you enter is sent anywhere
The fineness on this page is derived from the karat rather than stored, so it cannot disagree with the arithmetic. The mark is the published external figure.

Where this tool stops

Karat, fineness and percentage are definitional and never change. Everything involving money depends on the rate, the charges and the deduction you enter — none of which are stored on this site, because they move constantly. Hallmarking law and the legal minimum karat differ by country; check your national assay office before relying on a stamp.

Explained in our guides

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Frequently asked questions

What percentage of gold is 18K?
75.00% by weight. That is 18 parts gold in 24, or 750.00 parts per thousand, which is why it carries the 750 mark.
Why is 18K stamped 750?
Here the arithmetic lands exactly on the mark, so 750 needs no rounding at all.
How much pure gold is in a tola of 18K?
8.748 grams, out of 11.6638 grams gross. A tola is 180 troy grains, which is exactly three eighths of a troy ounce.
Where is 18K the standard?
Italy, Switzerland, France, luxury brands worldwide. National standards are conventions rather than properties of the metal, which is why a piece bought in one country often does not match one bought in another.
Is karat the same as carat?
No. Karat is this purity ratio out of 24. Carat is a mass unit for gemstones, exactly 0.2 grams. American English often spells both the same way, which is where the confusion comes from.
Are there any usage caps on the 18K Gold Purity?
No charge and no sign-up. There is no free tier to run out of because there is no paid tier — inputtesthub.com is funded by advertising rather than by metering the page.
Can you see what I put into this page?
No. The 18K Gold Purity runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
Who is the 18K Gold Purity for?
In practice it gets used for three things: reading a 750 hallmark and knowing what it guarantees. Working out the gold content of a 18K piece. Comparing 18K against the other standards before buying. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Where does the 18K Gold Purity stop being reliable?
Karat, fineness and percentage are definitional and never change. Everything involving money depends on the rate, the charges and the deduction you enter — none of which are stored on this site, because they move constantly. Hallmarking law and the legal minimum karat differ by country; check your national assay office before relying on a stamp. Knowing where a tool stops being trustworthy matters more than the cases where it works.
What are the key numbers for the 18K Gold Purity?
Fineness is 750.00 parts per thousand. Gold content is 75.00% by weight. Hallmark is 750. These are printed on the page itself, so you do not have to take them on trust.
Is the number rounded?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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