Calculate gold weight in grams, troy ounces, and pennyweights. Karat purity analysis with value estimation for coins, bars, and jewelry.
Gold is measured differently from most materials. Precious metals use the troy ounce, which is heavier than the everyday ounce, and karat tells you how much of the item's mass is actually gold. This calculator handles those conversions directly.
Enter a gold item's mass in grams, kilograms, troy ounces, avoirdupois ounces, pounds, or pennyweights, then choose the karat purity. The page reports the total mass, pure gold content, alloy content, volume, and an estimated value based on the current gold price.
For coins and bars, you can also enter dimensions to see whether the stated mass is consistent with the object's geometry. That makes the page useful for jewelry, bullion, and appraisal checks.
Gold pricing depends on the unit system as much as on the spot price. A small mismatch between grams, troy ounces, and purity can change the value materially, so keeping the conversions and valuation together is the main reason to use this page.
Pure gold mass = Total mass × Karat purity fraction. Troy ounces = grams / 31.1035. Pennyweights = grams / 1.55517. Value = Troy ounces (pure) × Price per troy oz. Volume = Mass / Density.
Result: 1.000 troy oz, $2,347.65
A 31.103 g coin at 24K (99.9%) contains 31.072 g pure gold = 0.999 ozt. Value = 0.999 × $2,350 = $2,347.65.
| Unit | Grams | Troy Ounces | |---|---|---| | 1 gram | 1.000 | 0.03215 | | 1 troy ounce | 31.1035 | 1.000 | | 1 avoirdupois ounce | 28.3495 | 0.9115 | | 1 pennyweight (dwt) | 1.5552 | 0.05000 | | 1 tola | 11.6638 | 0.37500 | | 1 tael (Chinese) | 37.429 | 1.20337 | | 1 baht (Thai) | 15.244 | 0.49000 |
The karat system divides gold into 24 parts. Pure gold is 24/24 = 100%. Each karat represents 4.167% gold content. Common alloys:
- **24K**: 99.9% gold; investment bars and coins - **22K**: 91.7% gold; coins (Krugerrand, Sovereign) - **18K**: 75.0% gold; fine jewelry (Europe, Asia) - **14K**: 58.3% gold; standard US jewelry - **10K**: 41.7% gold; minimum legal "gold" in the US
The remaining percentage consists of other metals: copper gives rose/red tones, silver produces green gold, nickel or palladium makes white gold.
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1 troy ounce = 31.1035 g; 1 avoirdupois ounce = 28.3495 g. Troy ounces are about 10% heavier. Precious metals are always traded in troy ounces.
A standard "Good Delivery" bar weighs 400 troy ounces (12.4 kg). At $2,350/oz, it is worth about $940,000.
Commercially, 24K is 99.9% pure (three nines fine). Ultra-high purity gold (99.99% or 99.999%) exists but is used only in electronics and research.
Pure gold is too soft for everyday wear. Alloys with copper, silver, or palladium add hardness. 14K and 18K are the most common jewelry alloys.
A pennyweight (dwt) = 1/20 troy ounce = 1.555 g. It is commonly used by jewelers in the US for pricing gold jewelry.
Common methods include acid testing, specific gravity testing (gold is very dense at 19.3 g/cm³), and electronic gold testers. Professional assay is the most accurate.