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: the standard unit is the troy ounce (31.1035 g), not the avoirdupois ounce (28.35 g). Karat indicates purity—24K is 99.9% pure gold, while 14K is only 58.3% gold by weight. This calculator handles all the conversions.
Enter the weight of a gold item in any unit—grams, kilograms, troy ounces, avoirdupois ounces, pounds, or pennyweights—and select the karat purity. The calculator instantly shows total mass, pure gold content, alloy content, volume, and an estimated market value based on the current gold price.
For coins and bars, enter physical dimensions to verify the stated weight against known geometry. The karat comparison table shows how the same item would be valued at every standard karat, making it invaluable for jewelers, pawn shops, refiners, and gold investors. Check the example with realistic values before reporting. Use the steps shown to verify rounding and units. Cross-check this output using a known reference case.
Gold transactions require precise unit conversions: buyer and seller must agree on troy ounces, purity, and price. A simple gram-to-troy-ounce error can mean hundreds of dollars on a single deal.
This calculator prevents costly mistakes by handling all conversions in one place, and the karat comparison table gives instant insight into how purity affects value—essential for buying, selling, or appraising gold jewelry and bullion.
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.
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. Aloys 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.