Gold Karat Converter — Calculate Equivalent Weight Between All Karats

Convert weight between different gold karats (24, 22, 21, 18, 14...) with accurate explanation of ratios and calculation steps

Full Gold Karat Conversion Table

Use the following table for quick conversion between all karats. To calculate your gold value in local currency, use the gold value calculator with the current gold prices.

Ratios indicate conversion factor from row (from) to column (to). Numbers shown as % for quick reference.
From ↓ \ To → 24k 22k 21k 18k 14k 10k 9k
24k 100%109.1%114.3%133.3%171.4%240%266.7%
22k 91.7%100%104.8%122.2%157.1%220%244.4%
21k 87.5%95.5%100%116.7%150%210%233.3%
18k 75%81.8%85.7%100%128.6%180%200%
14k 58.3%63.6%66.7%77.8%100%140%155.6%
10k 41.7%45.5%47.6%55.6%71.4%100%111.1%
9k 37.5%40.9%42.9%50%64.3%90%100%
Quick example: 100g of 21k → 24k = 100 × 0.875 = 87.5 g of 24k

Why Do We Need to Convert Gold Karats?

Converting gold karats is not just a mathematical exercise — it is a practical necessity in daily life when dealing with gold. Here are the most important situations where conversion is needed:

🏪

When Buying or Selling

You have 100g of 21k gold and want to know how much it equals in 24k to calculate the true value. Shops calculate prices based on pure gold (24k). Use the sell calculator or the buy calculator with the converter.

🔄

Exchanging Gold Pieces

You want to exchange an 18k piece for a 21k piece. The shop will calculate the equivalent weight in pure gold to ensure a fair exchange. 100g of 18k = 75g of 24k = 85.7g of 21k.

🎁

Gifts and Inheritance

You inherited gold in different karats (24, 21, 18) and want to know the total value in a unified karat. Conversion helps you add the weights correctly and use the value calculator.

📊

Calculating Zakat

Zakat is calculated on pure gold (24k). If you have 21k or 18k gold, you must convert it first to find the true weight of pure gold. Use the zakat calculator after conversion.

💍

Remelting and Remanufacturing

You want to convert your old gold into a new piece at a different karat. The shop will take the pure gold weight and reshape it. Example: 100g 21k → 87.5g 24k → 73.3g 18k after adding metals.

✈️

Travel and Customs

Some countries set the allowed gold import limit by pure gold weight (24k). If you have gold in different karats, you must calculate the equivalent 24k weight to avoid customs problems.

Important tip: Understand the difference between weight and value

Weight increases when converting to a lower karat, but value stays the same (without making charges). Example:

  • 100 g of 24k = value 52,420 Riyal (at price 524.2 Riyal /gram)
  • = 114.3 g of 21k = same value 52,420 Riyal (at price 458.7 Riyal /gram)
  • = 133.3 g of 18k = same value 52,420 Riyal (at price 393.2 Riyal /gram)

💡 Conclusion: More weight does not mean more value! What matters is the amount of pure gold (24k) inside the piece. Use the current gold prices to calculate the final value.

Detailed Practical Examples

Convert 100g 21k → 24k

  • 21k purity = 21 ÷ 24 = 0.875
  • Pure gold = 100 × 0.875 = 87.5 grams
  • In 24k: 87.5 ÷ 1.000 = 87.5 grams
Result: 100g 21k = 87.5g 24k

Convert 50g 18k → 21k

  • 18k purity = 18 ÷ 24 = 0.75
  • Pure gold = 50 × 0.75 = 37.5 grams
  • In 21k: 37.5 ÷ 0.875 = 42.86 grams
Result: 50g 18k = 42.86g 21k

Convert 100g 24k → 21k

  • Pure gold = 100 × 1.00 = 100 grams
  • In 21k: 100 ÷ 0.875 = 114.29 grams
  • Added metals ≈ 14.29 grams
Result: 100g 24k = 114.29g 21k

Frequently Asked Questions

How do I convert 21-karat to 24-karat?
Multiply the weight by 0.875 (purity ratio). Example: 100g of 21k × 0.875 = 87.5g of 24k.
What is the conversion ratio from 18k to 24k?
Purity ratio 18÷24 = 0.75 (75%). So 100g of 18k = 75g of 24k.
Why does weight decrease when converting from a lower karat to a higher karat?
Because lower karats contain other metals (copper, silver). When converting to pure gold, these metals are removed, so the weight decreases.
How many grams of 24k does 100 grams of 21k equal?
100 × 0.875 = 87.5 grams of 24k.
Can gold actually be physically converted between karats?
Yes. You can raise the karat by removing other metals (melting and refining), and lower it by adding copper/silver.
What is the price difference between 24k and 21k?
24k contains 100% pure gold, while 21k contains 87.5% gold. Price of 21k = price of 24k × 87.5%.
Why is 21k the most common in Saudi Arabia?
Good balance between purity (87.5%) and hardness, suitable for everyday jewellery, reasonable price, and aligned with local traditions.
How do I calculate the purity ratio for any karat?
Purity = (karat ÷ 24) × 100%. Example: 18k = (18÷24)×100 = 75%.
Do all karats have the same colour?
No. 24/22/21k: golden yellow. 18k: can be yellow, white, or rose depending on added metals. 14k and below: various colours.
What happens when converting 100g of 21k to 18k?
100 × (21÷18) ≈ 116.7g of 18k; the weight increases because 18k contains more metals (25%).

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