What Is Gold Purity

What Is Gold Purity? Understanding Karats, Fineness and Gold Standards

Gold purity is the share of pure gold in an alloy, expressed in karats (parts per 24) or fineness (parts per 1,000). If you are asking what is gold purity, the short answer is this: 24K is pure gold, 18K is 75% gold, and a fineness of 750 means 750 parts of gold in every 1,000.

Pure gold is very soft, so jewellers mix it with metals such as copper, silver or palladium. These alloys are harder and can change the colour. The karat number tells you how much gold remains after mixing. A higher number means more gold and a softer piece.

The guide covers the formulas for converting karats to percentages and fineness, the Egyptian tradition of 21K gold (875 fineness), how hallmarks work, and a checklist for verifying a piece before you pay. It was written by the Dahab Zaman editorial team and draws on the World Gold Council, the LBMA and Wikipedia.

What Is Gold Purity? Understanding Karats, Fineness and Gold Standards

Gold purity is the share of pure gold in an item, shown as a percentage, as karats (parts of 24) or as fineness (parts per 1000). Jewellery generally uses karats, while bullion uses fineness.

Purity is separate from weight, which is measured in troy ounces (1 troy ounce = 31.1034768 grams).

What Is Gold Purity?

Gold purity is the proportion of pure gold in an item, measured by weight. It is usually stated in karats out of 24, or as fineness in parts per thousand.

Purity describes finished products, while grade describes gold ore. Karat (US) and carat (UK) both mean purity, whereas carat for gemstones measures weight.

What Makes Gold Pure?

Gold is pure when nothing else is mixed into it. 24K means all 24 parts are gold.

Refining reaches about 999.9 parts per thousand, so 1000 is only theoretical. In 1957 the Perth Mint refined 999.999 gold, the purest ever produced.

Pure Gold vs. Gold Alloys

An alloy is gold mixed with other metals, such as copper, silver, zinc, palladium or nickel.

18K is 75% gold and 25% other metals.

9K is 37.5% gold.

Lower karats hold less gold.

Why Is Gold Mixed with Other Metals?

Pure gold is soft, so alloying adds durability for jewellery worn daily.

Alloying also changes colour. Copper gives rose gold its pink tone, while palladium or silver produces white gold, which is usually rhodium-plated.

How Is Gold Purity Measured?

Gold purity is measured in two main ways: karats, which count gold parts out of 24, and fineness, which counts parts per 1000.

Understanding Gold Karats (K)

What is gold karat? It is the number of gold parts in 24 parts of metal, so 18K means 18 parts gold.

The formula is C = 24 × (Mg / Mm), so 18/24 = 75%.

Karat is the US spelling and carat the British one. Carat (ct) for gemstones measures weight instead.

Understanding Gold Fineness

Fineness is gold's share of total mass in parts per 1000: (pure metal ÷ total mass) × 1000. Stamps drop the decimal point, so .750 appears as 750.

Pure gold is marked 999.9, not 1000, because refining cannot remove every trace of impurity.

Gold Karat vs. Gold Fineness

Fineness is more precise, while karats are rounder commercial labels. Jewellery generally uses karats and bullion uses fineness.

14K is nominally 583, but European practice usually stamps it 585.

Gold Purity Chart: Comparing Different Gold Karats

A single chart sets each common karat beside its gold percentage, fineness mark and typical use. Commercially, 24K requires at least 99.95% purity.

KaratGold %Fineness markTypical use24K99.9%+999.9Bars, coins22K91.67%916Traditional jewellery, coins21K87.5%875Egyptian jewellery18K75%750Fine jewellery14K58.3%585Everyday jewellery10K41.7%417Budget jewellery9K37.5%375Budget jewellery

24K Gold: 99.9%–99.99% Purity

24K gold is practically pure, marked 999 or 999.9. It is soft and deep yellow, so it is used mainly for bars and coins.

22K Gold: 91.67% Purity

22K gold has a fineness of 916 and balances rich colour with some added strength.

It is used in British Sovereigns, Krugerrands and American Gold Eagles.

It is the standard jewellery karat in some countries, such as India.

21K Gold: 87.5% Purity

21K gold is 21/24 = 0.875 pure, so it is marked 875. It is the traditional Egyptian jewellery karat.

18K Gold: 75% Purity

18K gold is marked 750 and is typical across most of Europe. It is the highest fineness commonly used for gemstone jewellery, because stones need harder metal to stay secure.

For a closer comparison of these two popular jewellery options, read Difference Between 18K and 21K Gold.

14K and 10K Gold

Lower karats such as 14K and 10K contain more alloy metal and are tougher.

14K is nominally 58.3%, stamped 585, and most common in the United States.

10K is 41.7% gold, the US legal minimum to be called gold.

Legal minimums vary: 9K in the UK and France, 8K in Denmark and Greece.

What Karat Is Pure Gold?

If you ask what karat is pure gold, the answer is 24K, or practically 999.9 fineness. A 23K or 22K piece still contains other metals, so it is not called pure.

How to Calculate Gold Purity

Gold purity is worked out with simple division and multiplication. Each method below converts one unit into another.

Calculate Gold Purity from Karats

Karats show how many parts out of 24 are gold, so the conversion takes three steps.

Divide the karat number by 24.

Multiply by 100 to get the percentage.

Multiply the fraction by 1000 to get fineness.

For 21K, 21 ÷ 24 = 0.875, or 87.5%, which gives a fineness of 875. For 18K, 18 ÷ 24 = 0.75, or 75%.

Calculate Gold Purity from Fineness

Fineness is parts per thousand, so divide by 1000 for the fraction, then multiply by 24 for karats.

Divide the fineness by 1000.

Multiply the fraction by 24.

A stamp of 750 gives 0.75, and 0.75 × 24 = 18K. A stamp of 585 gives 14.04K, which is why 14K jewellery is usually stamped 585 instead of 583.

Calculate Pure Gold Content by Weight

Pure gold content is the total weight multiplied by the purity fraction.

Weigh the item.

Convert its purity to a fraction.

Multiply the weight by the fraction.

For 10 g of 21K, 10 × 0.875 = 8.75 g of fine gold. For a bar, 400 oz × 0.9999 = 399.96 fine ounces.

Why Does Gold Purity Matter When Buying Gold?

Gold purity determines how much real gold you pay for, how the piece wears, and what it fetches when resold.

How Purity Affects Gold Prices

Gold is priced per troy ounce of fine gold, so value rests on pure content. In Egypt, you pay the daily karat rate times the weight, plus the masna'iyya labour fee. Check Gold Prices in Egypt Today before comparing quotes.

How Purity Affects Durability and Strength

Purity changes how gold behaves in daily wear.

A higher karat means a softer metal that scratches and bends more easily.

A lower karat is harder, but contains more alloy metals.

How Purity Affects Gold Color

Higher purity gives a richer yellow. Copper adds a pink tone, while palladium or silver lightens it. White, rose and yellow gold of the same karat hold the same gold percentage.

How Purity Affects Resale Value

Resale value is based on verified fineness and weight. A hallmark and receipt support the valuation, while labour fees are usually not recovered. To understand how these labour costs are calculated, see How to Calculate Gold Making Charges.

What Is the Difference Between 24K, 21K and 18K Gold?

The main difference between 24K, 21K, 18K and 14K gold is the share of pure gold in each alloy. That share determines hardness, colour and ideal use.

Anyone asking what karat gold is best should first decide whether the piece is for wear or for saving.

KaratPurityHardnessColourBest use24K99.9%+Very softDeep yellowBars, coins, investment21K87.5%ModerateRich yellowTraditional Egyptian jewellery18K75%HardWarm yellowStone-set rings, fine jewellery14K58.3%HardestPaler yellowDaily wear, budget rings

Pure 24K gold is too soft for most jewellery, because it scratches and bends easily.

24K vs. 21K Gold

24K is 99.9% or more gold, while 21K is 87.5%, a gap of about 12 points. That makes 21K firmer for daily jewellery, while 24K suits bars and coins.

21K vs. 18K Gold

21K holds 87.5% gold against 75% in 18K. The 18K alloy is harder and holds stones better. It also costs less per gram, as it contains less gold.

24K vs. 18K Gold

The widest purity gap among common jewellery karats lies between 24K at 99.9% and 18K at 75%. 24K is soft and intensely yellow, so it is kept for bullion, while 18K is firmer and better for gem-set jewellery.

Which Gold Karat Is Better for Investment?

Bullion with a fineness of 995 to 999.9 is the stronger choice for saving. Jewellery karats add labour costs that are not recovered on resale.

What Karat Gold Is Best for Everyday Use?

For people asking what karat gold is best for everyday use, 18K or 14K is usually preferred because both resist scratches. 21K remains the traditional Egyptian choice.

Nickel in some alloys can cause skin reactions.

If your skin is sensitive, ask the jeweller which metals are in the alloy.

What Karat Gold Is Best for Rings?

When choosing what karat gold is best for rings, 18K is the highest fineness normally used for stone-set pieces. The metal must be hard enough to hold the stone.

14K offers greater durability at a lower cost.

18K offers a richer colour and higher gold content.

What Is Better, 14K or 18K Gold?

Deciding what is better, 14K or 18K gold, depends on budget and wear. 14K holds 58.3% gold and 18K holds 75%.

Cost: 14K is cheaper.

Durability: 14K is tougher.

Colour: 18K is richer.

Skin: 18K is less likely to contain nickel.

Stones: both work, though 18K is the usual ceiling.

How to Check Gold Purity and Identify Genuine Gold

No single test proves gold is genuine. Reliable verification combines the hallmark, written documentation and professional testing.

Understanding Gold Hallmarks and Purity Stamps

A purity stamp is a small mark on the piece stating its karat or fineness.

Common stamps are 375, 585, 750, 916 and 999.

UK hallmarks use a three-figure fineness, and gold items over 1 g, apart from coins and pure gold bars, must carry one.

A stamp alone proves little without a trusted maker behind it.

Gold Purity Testing Methods: XRF, Fire Assay and Acid Testing

Fire assay is the reference method for official certification, while XRF is the usual routine check.

Fire assay: the most accurate laboratory method.

XRF: non-destructive, but it reads only the surface.

Magnet and water tests: not conclusive.

How to Verify Gold Bars and Coins Before Buying

Verifying a bar or coin means matching its markings with documents you can check.

Check the stated fineness, such as 999.9, or the 995 Good Delivery minimum.

Compare the weight and markings with the certificate, and ask for assay documentation.

For buyers comparing available investment products, Dahab Zaman offers Gold Coins and Gold Cast Bars. You can also compare products from SAM Gold and BTC Gold.

Gold Purity Standards and Hallmarking in Egypt

Egyptian practice centres on 21K gold, stamped 875, with 18K and 24K sold alongside it. Each karat has its own fineness stamp.

Common Gold Karats in the Egyptian Market

Four karats are sold in Egypt, and 21K is the one buyers have long preferred for jewellery.

18K, 21K, 22K and 24K are all available.

24K appears mainly as bars and coins.

Each karat has its own price per gram, so check Today's gold prices before you shop.

What Is the Egyptian Gold Hallmark?

The Egyptian hallmark is the official assay authority's stamp, with a fineness number such as 875 for 21K and 750 for 18K.

Read the number as parts per thousand: 875 means 87.5% gold. Check that the stamp matches the karat on your invoice.

How to Buy Gold with Verified Purity in Egypt

The price is the day's rate for the karat multiplied by weight, plus a labour fee. Only the labour fee is negotiable. Buying gold in Egypt is safest from transparent sellers such as Dahab Zaman.

Confirm the Gold price today in Egypt for your karat.

Check the karat stamp, weight and labour fee.

Get an itemised invoice.

Ask about return and buy-back terms.

For high-value items, request independent testing, since magnet and XRF checks have limits.

Which Gold Purity Is Best for Investment?

The best purity for investment gives the most fine gold for the least extra cost. That means high fineness and a low labour premium.

Is 24K Better for Investment Than 21K?

Yes, for pure investment, 24K is usually the better choice. It holds the most gold per gram and carries lower making charges.

21K suits savers who also want to wear what they own. The labour cost paid at purchase is not recovered as metal value.

Why Are 999.9 Gold Bars Used for Investment?

Bars at 999.9 fineness are the standard store of value in bullion, because their purity is easy to verify and compare.

999.9 is the most popular bullion fineness.

Good Delivery bars need a minimum fineness of 995.

Their weight must be 350 to 430 fine troy ounces.

To understand the stages involved in producing these investment products, read Gold Bar Manufacturing Process.

Are 21K Gold Coins Suitable for Saving?

They can be, especially for small, regular savings. A 21K coin holds 87.5% gold and is familiar to Egyptian savers, so it is easy to sell.

Resale value depends on verified weight and purity, so keep the original packaging and paperwork.

What to Check Before Buying Gold Bars or Coins?

Verify the item before you pay, then compare the price with the market. Dahab Zaman suggests this checklist:

The fineness mark on the bar or coin

The stated weight

A certificate

Sealed packaging

The seller's documentation

Today's gold prices, plus any stated premium

Frequently Asked Questions About Gold Purity

What is gold purity?

Gold purity is the proportion of pure gold in an alloy, expressed in karats out of 24 or as fineness in parts per thousand. Knowing what is gold purity helps you read stamps such as 750 or 875 correctly.

What is the purest form of gold?

The purest gold in commercial production is 999.99 fineness, while 999.9 is the most popular bullion grade. Refiners cannot reach exactly 100%, so even 24K gold carries a very small trace of other elements.

Is 24K gold 100% pure?

No, 24K gold is practically pure but not exactly 100%. Refining limits mean it is stamped 999 or 999.9, and as a commercial designation, 24K is permitted from a minimum of 99.95% purity.

What is the difference between 999 and 999.9 gold?

999 gold is 99.9% pure, while 999.9 gold is 99.99% pure. The extra nine means only 0.01% impurities instead of 0.1%, which is why 999.9 is called “four nines fine”.

How many karats is pure gold?

Pure gold is 24 karats, meaning 24 parts out of 24 are gold. In practice, it is stamped 999 or 999.9, because gold can only be refined to about 999.9 parts per thousand.

What does 875 mean on gold?

The stamp 875 means the piece is 87.5% gold, which equals 21K. It comes from 21 ÷ 24 = 0.875. This is the karat Egyptian buyers have long preferred for jewellery.

Is 21K gold real gold?

Yes, 21K gold is real gold, containing 87.5% pure gold alloyed with other metals such as copper or silver. The alloy makes it harder than 24K, so it holds up better as jewellery.

What is the difference between 21K and 18K gold?

21K gold is 87.5% pure and 18K is 75% pure. The 21K piece has a richer yellow colour and higher gold content, while 18K contains more alloying metals and is harder, which suits stone-set rings.

How do I calculate gold purity?

Divide the karat by 24 to get the percentage, so 18 ÷ 24 = 0.75, or 75%. From fineness, divide by 1000. For pure gold content, multiply the weight by the purity: 10 g of 21K holds 8.75 g.

How can I check gold purity at home?

Start by reading the purity stamp, such as 750 or 875, with a magnifying glass, then try a magnet, since gold is not magnetic. These checks are only basic and not foolproof, so rely on an XRF or acid test for certainty.

Does higher gold purity mean better quality?

No, higher purity means more gold, not necessarily better quality for every use. Pure 24K is very soft, so lower karats such as 18K or 14K resist scratches and bending better in daily jewellery.

Why is 24K gold softer than 18K?

24K gold is softer because it has no harder metals mixed in. In 18K, 25% of the alloy consists of metals such as copper or silver, which strengthen the structure. Pure 24K can even be scratched with a fingernail.

Which gold purity is best for investment?

For investment, bars and coins of 995 to 999.9 fineness are the standard. Good Delivery bars must be at least 995, and their value rests on pure gold content, since prices are quoted per troy ounce of fine gold.

Is 999.9 gold suitable for jewelry?

It is suitable only for occasional or ceremonial pieces, not daily wear. At 999.9, gold is very soft and scratches or bends easily, so everyday rings and bracelets are usually made in 21K, 18K or 14K.

Final Thoughts: Understanding Gold Purity Before You Buy

Gold purity is read on two scales: karats out of 24 and fineness out of 1000. In Egypt, 21K (875) is the familiar jewellery standard, while 999.9 marks investment bars. Check the hallmark and Today's gold prices first. Shop now at Dahab Zaman.