What is a gold ounce, and how do you get the 18k gram price?
A gold ounce is a troy ounce, the world’s standard unit for gold, and it weighs exactly 31.1034768 grams. To get the price of one gram of 18k gold, divide the ounce price by 31.1034768 and multiply by 0.75; for your own currency, multiply by its rate per US dollar. Below we walk through the formula with an example and explain why local prices rarely match it.
What is a troy ounce?
A troy ounce is the unit used to weigh and price precious metals worldwide, and it equals 31.1034768 grams, usually rounded to 31.1035. When the news quotes “the gold price”, it means the price of one troy ounce of pure gold in US dollars.
Don’t confuse it with the everyday ounce used for food, which is about 28.35 grams. If you used that one, your gram price would be off by roughly 10 percent.
Karats: why 18k means 750 parts per 1000
A karat number tells you how much of a piece is pure gold. 18k gold is 18 parts gold out of 24, which is 750 parts per 1000 or 75 percent; the rest is metals such as copper and silver that make it harder and more durable.
The global ounce price is for pure gold, so for 18k you multiply by 0.75. Common purities:
- 24k: practically pure gold, as in bars
- 22k: about 916 parts per 1000, common for coins and jewellery in some countries
- 21k: 875 parts per 1000
- 18k: 750 parts per 1000, very common for jewellery
The ounce-to-gram formula
In short: price per gram of 18k = ounce price ÷ 31.1034768 × 0.75. The result is in US dollars; for your own currency, multiply it by that currency’s rate per dollar. Step by step:
- Take the global price of one ounce of gold in US dollars.
- Divide by 31.1034768 to get the price of one gram of pure (24k) gold.
- Multiply by 0.75 to get the price of one gram of 18k gold.
- Multiply by your currency’s rate per US dollar.
A worked example with made-up numbers
Suppose the ounce is $3,000. This figure is only a round number for the example, not today’s price; see the gold price page for the live value.
- One gram of pure gold: 3,000 ÷ 31.1034768 = about $96.45
- One gram of 18k gold: 96.45 × 0.75 = about $72.34
- In another currency: if one dollar were 3.67 units of it, 72.34 × 3.67 = about 265.5 units
Why local gold prices differ from the formula
The formula gives the global value of the gold itself, not what a jeweller charges you. The gap comes from a few things:
- Local premium: when local demand is high, prices can run ahead of the global value, and sometimes they lag behind. In Iran this gap is often called the “bubble”.
- Exchange rate: the local market may use a different dollar rate from the one you used.
- Making charges: for jewellery, the work of making the piece is charged on top of the gold.
- Taxes: VAT or other taxes, depending on the country and the type of gold.
- Dealer margin: a shop sells a little above and buys back a little below the value.
Gold prices in Waletifi
Waletifi’s gold section uses the same logic: its price follows the global gold price, and your balance is shown in grams of 18k and in your own currency. The gold is tokenized gold backed by physical gold, where one full token represents one troy ounce, and it sits in your own wallet.
Every buy and sell uses a signed quote that shows the price and the fee before you confirm. The gold section depends on your country and may not be available everywhere.
