How to Calculate Gold Value by Karat: A Step-by-Step Guide
Published June 19, 2026 · updated June 19, 2026
If you’ve ever stared at a piece of gold jewelry and wondered what it’s actually worth, the good news is the math is straightforward once you understand karat purity. Gold value is simply the live spot price multiplied by purity, multiplied by weight. Here’s how to do the calculation correctly.
Understand karat purity
Karat (k) measures how much of a piece, by weight, is pure gold versus alloy metals like copper, silver, or zinc. Pure gold is 24 karat, which is 99.9% gold. Each karat represents 1/24 of the whole:
- 24k = 99.9% pure (0.999)
- 22k = 91.67% pure (0.9167)
- 18k = 75% pure (0.75)
- 14k = 58.5% pure (0.585)
- 10k = 41.67% pure (0.4167)
A 14k ring is not “mostly gold” — it is only 58.5% gold by weight. The rest is alloy. This is the single biggest factor people overlook when estimating value.
Get the live spot price
Gold trades globally per troy ounce, and one troy ounce equals 31.1034768 grams. To convert a per-ounce price to a per-gram price, divide by 31.1034768. If spot gold is $2,400 per ounce, the gram price is roughly $77.15. Use a fresh spot price — gold moves daily, and an old quote can throw your estimate off by a meaningful amount.
The core formula
For any item, the melt value is:
Spot price per gram × purity × weight in grams = gold value
Worked example for a 14k gold chain weighing 10 grams at a $2,400/oz spot price:
- Spot per gram: $2,400 ÷ 31.1034768 = $77.15
- Multiply by purity: $77.15 × 0.585 = $45.13 per gram of 14k
- Multiply by weight: $45.13 × 10 g = $451.30 total melt value
That number is the melt value — the raw metal worth. It is not what a dealer will pay you; expect offers of 70–90% of melt from reputable buyers, with pawn shops and mail-in services often at the lower end.
Working in pennyweights
Many US dealers quote in pennyweights (dwt), where 1 dwt = 1.55517 grams (1/20 of a troy ounce). To convert grams to dwt, divide grams by 1.55517. Our 10-gram chain is about 6.43 dwt. Just make sure you compare quotes in the same unit.
Verify before you sell
- Weigh on a digital scale that reads to 0.01 gram; kitchen scales are usually too coarse.
- Confirm the karat stamp, but remember stamps can be inaccurate or faked. Acid testing or an XRF scan from a jeweler is more reliable.
- Run the numbers yourself before accepting any offer. A trustworthy buyer will show you the spot price and the math they used.
Skip the manual arithmetic and use the gold calculator to get an instant estimate, or check the live rate on the 14K gold price per gram page.
Frequently asked questions
- Does higher karat always mean more value? Yes, for the same weight. An 18k piece is worth more than a 14k piece of identical weight because it contains a higher percentage of pure gold.
- Why is my jeweler’s quote lower than my calculation? Dealers pay below melt value to cover refining, profit, and risk. A fair offer is typically 70–90% of melt.
- Do gemstones add to the gold value? No. This formula covers only the metal. Stones must be valued separately, and many buyers deduct a fee to remove them.