Gold Karat to Purity Explained

Gold karat tells you how much of an item is actually gold. The higher the karat, the larger the pure-gold share and usually the higher the raw gold value at the same weight.

Written by Calzivo Team

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Gold karat tells you how much of an item is actually gold. 24K is almost pure gold, while 22K, 18K, 14K, and 10K contain progressively less gold and more alloy metals. That is why two items with the same weight can have very different raw gold values.

Use the calculators: Try the Gold Calculator for gross metal-content value, or the Scrap Gold Calculator for gross melt value and an optional user-entered payout scenario.

Helpful tools: Currency Converter and Unit Converter.

Karat to purity table

Karat to purity table - Karat, Purity, What it means
Karat	Purity	What it means
24K	99.9%	Almost pure gold
22K	91.67%	Mostly gold with a small alloy share
18K	75.0%	Three-quarters gold, often used in jewelry
14K	58.33%	Moderate gold content with more alloy metals
10K	41.67%	Lower gold content, more alloy than higher-karat pieces

Why higher purity changes value

The raw value of gold comes from the pure-gold portion, not the total item weight alone. If two rings both weigh 10 grams, the 24K ring contains far more pure gold than the 14K ring. That means the 24K item will usually show a much higher raw value when you use the same spot price.

This is also why karat matters so much in scrap value discussions. Buyers do not pay for alloy metals the same way they pay for gold content. First they estimate pure gold content, then they apply spot value and any dealer or refining deductions.

Simple examples

A 10 g piece of 24K gold contains about 9.99 g of pure gold.
A 10 g piece of 18K gold contains 7.5 g of pure gold.
A 10 g piece of 14K gold contains about 5.83 g of pure gold.

The total item weight is the same in each example, but the gold content changes dramatically. That difference is what the calculators turn into a value estimate.

Practical note: Raw gold value is not always the same as a retail jewelry price or a scrap payout. Retail prices can include making charges and taxes. Scrap payouts can be lower because of dealer or refining fees.

Karat ratios and calculator fineness presets

The educational karat ratio is karat divided by 24. The Calzivo calculators instead apply the exact marked-fineness preset displayed in the selector: 999, 916, 750, 585, or 417 parts per thousand. That is why a 14K preset uses 58.5%, while the unrounded 14 / 24 ratio is approximately 58.3333%. Neither a label nor a preset verifies the composition of an item.

Formula

Purity fraction = karat / 24

Multiply by 100 to express the ratio as a percentage. Keep the unrounded fraction for manual calculations.

Formula

Pure-gold weight = gross weight x purity fraction

Use actual tested fineness when it is available instead of assuming a nominal karat ratio.

18K substitution

For 10 g of 18K gold, purity fraction = 18 / 24 = 0.75 and pure-gold weight = 10 x 0.75 = 7.5 g.

14K substitution without premature rounding

For 20 g at the theoretical 14 / 24 ratio, pure-gold weight = 20 x 14 / 24 = 11.666666... g. At an entered pure-gold price of 65 per gram, gross value is approximately 758.33. The calculator 14K (585) preset is a different marked-fineness assumption and produces 11.7 g of pure-gold equivalent.

Hallmarks, testing, and value limits

A karat or fineness mark is evidence to inspect, not a laboratory result produced by Calzivo.
Plating, filling, solder, stones, clasps, and other materials can make total item weight unsuitable for a solid-gold calculation.
The calculators do not supply a live gold price, perform an assay, convert currencies, or provide an appraisal or buyer offer.
Market prices and commercial payout policies can change; professional testing or transaction verification may be appropriate.
Results are educational estimates, not financial, investment, tax, legal, appraisal, or selling advice.

Frequently asked questions

How do I convert karat to a purity fraction?

Divide karat by 24. For example, 18 / 24 = 0.75. Multiply by 100 for 75%.

Why does the calculator show 14K as 585 fineness?

The calculator uses its displayed marked-fineness preset, 585 parts per thousand. The theoretical 14 / 24 ratio is approximately 583.333 parts per thousand.

Is 24K always exactly 100% pure?

No calculator assumption proves that. Calzivo uses the displayed 24K (999) preset, while actual composition requires reliable testing.

Does a hallmark guarantee what this calculator should enter?

Calzivo does not verify hallmarks or composition. Check applicable hallmark evidence and obtain professional testing when authenticity or composition matters.

Does higher karat guarantee a higher sale price?

No. Higher purity increases pure-gold content at the same gold-bearing weight, but actual price can also depend on testing, market movement, item condition, design, and buyer policy.

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