Fake coins are a common problem for collectors. A simple density check can help you test a claim about a coin. Enter the weight and volume of your coin below to calculate its density.
How it works
Compare the density of the coin with the known density of the metal it is claimed to be. For example, if a coin is said to be old and made of pure gold, its density should be close to 19.3 g/cm³. Fake gold coins are often gilded on the outside with a cheap metal core, and a density check can expose this. Remember Archimedes.
- Find the weight. Use a weighing balance. Grams are a convenient unit for a coin.
- Find the volume. Take a graduated measuring cylinder, narrow enough to be accurate but wide enough for the coin to fit inside. Fill it with distilled water to a known mark, say 50 ml in a 100 ml cylinder. Drop the coin in and note the new level. If the water now stands at 60 ml, the coin’s volume is 10 ml, or 10 cm³ (1 ml = 1 cm³).
- Calculate. Enter the weight and volume in the calculator. The density is given in g/cm³.
- Compare. Check the result against the reference density of the metal. You can find densities of various metals and alloys in this table.
Example
Weight of coin: 77.2 g. Volume of coin: 4 ml. The calculator gives 19.3 g/cm³, which is the density of gold, so this coin is consistent with being gold.
Estimates only, not a valuation or authentication.
Image credit: “Shivrai Hon 01 (cropped)” by Pratishkhedekar, via Wikimedia Commons, licensed under CC BY-SA 4.0.