Measure a coin's density

NumisdocTips & tools

Written on March 26, 2011 • Last edit: April 10, 2011
See the French articleComments (7)

Measuring density is one way for telling what metal a coin is made of. A coin density is the ratio between the coin's weight and the weight of the same volume of water. Density is specific of the metal. This density way better works for pure metals (silver, gold, zinc...) and for heavier coins. Regarding silver coins, the density method can tell the fineness.


Density measurement requires:
  • a precision scale (0.01 g)
  • a glass filled with water
  • a paper clip
  • a piece of string, 10 to 20 cm long


  1. Weight the coin and write down its weight [1].
  2. Tie the string to the paper clip.
  3. Put the glass of water on the scale.
  4. Put the clip fully under water while suspended to the string. Make sure the clip makes no direct contact with the glass.
  5. Set the scale tare (set it to 0).
  6. Put the coin in the clip. If the coin is too large, bend the clip and set the coin on top of it.
  7. Put the coin and clip fully under water. Make sure they make no direct contact with the glass.
  8. Write down the new weight displayed on the scale [2].


You'll find the density by dividing the coin's weight [1] by the additional weight when the coin is in the water [2].

Coin's weight [1] Additional weight
when coin in water [2]
÷ = ?

This density way may not be accurate. You should not fully trust its result and only rely on it.

It addition, you might want to test the coin with a magnet. If the coin moves toward the magnet it has to be nickel, iron or steel. If not, it is another metal or alloy.