What is Millesimal Fineness in Gold? Understand the Meaning of 375, 750, and 800

In mathematics, the term millesimal fineness (permilagem) is the expression of a fraction of 1000 that is, a way of measuring fractions of values in proportion based on one thousand.

Millesimal fineness is widely applied in statistical or measurement data such as birth rates, death rates, water salinity, the purity of precious metals, housing, and more. The symbol for millesimal fineness is ‰.

The most common application of proportional values in our daily lives is percentage % (base one hundred). However, when greater precision and a better sense of values are required, millesimal fineness is applied (per thousand).

What does "millesimal fineness" mean in gold?

In gold, the number indicated before the fineness represents the amount of pure gold per every 1000 parts.

Let’s look at the designation of gold in Portugal. The so-called Portuguese Gold (19.2 Karats) has a fineness of 800. This means that in every 1000 parts, 800 of those parts correspond to pure gold and 200 parts correspond to other materials.

International Gold (18 Karats) has a fineness of 750, which means 750 parts of pure gold and 250 parts of other materials.

In the case of 9-Karat gold (375 fineness), can you understand how much pure gold it contains and how much consists of other materials?

So, for you, which is better? Portuguese Gold or International Gold? We should not confuse millesimal fineness with parts per million (ppm), which is based on one million.

Do you know what the assay marks (hallmarks) on precious metal pieces are?

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