22K to 18K table
| 22K weight | 18K gold made | Alloy added |
|---|---|---|
| 1 g | 1.22 g | 0.22 g |
| 5 g | 6.11 g | 1.11 g |
| 10 g | 12.22 g | 2.22 g |
| 20 g | 24.44 g | 4.44 g |
| 50 g | 61.11 g | 11.11 g |
| 100 g | 122.22 g | 22.22 g |
The formula
18K weight = 22K weight × 22 ÷ 18. Ten grams of 22K becomes 12.22 g of 18K with 2.22 g of alloy added.
Why jewellers make stone settings in 18K
Prongs and bezels that hold diamonds need a harder metal than 22K. At 75% gold, 18K is strong enough for settings yet still rich in colour, so old 22K gold is sometimes alloyed down to 18K when it is remade into a ring with stones.
The alloy also decides the colour: more copper gives rose gold, while white gold uses palladium or nickel and is usually plated with rhodium.
Value per gram
A gram of 18K contains 0.75 g of gold against 0.9167 g in 22K, so 18K is worth about 81.8% of the 22K price per gram by metal content.
Calculated with karat ÷ 24 (22K = 91.67%). Hallmarks round slightly differently (916, 750, 585); switch the calculator to the hallmark basis to match a buyer who prices by the stamp.
Frequently asked questions
How much 18K gold do I get from 10 grams of 22K?
12.22 grams, after adding 2.22 g of alloy.
Which is better, 18K or 22K?
22K has more gold and a deeper yellow colour, so it holds more value per gram. 18K is harder and keeps stones more securely. Plain bangles and chains are usually 22K; diamond and gemstone jewellery is usually 18K.
What hallmark does 18K gold have?
750, meaning 750 parts of pure gold per 1,000.