Coin Specific Gravity & Water Test Calculator
Non-destructively assay unknown silver and gold coins using Archimedes’ underwater displacement principle. Calculate exact density in g/cm³, estimate millesimal fineness, and expose base-metal or tungsten cores.
Archimedes Specific Gravity & Alloy Assay Lab
What is your hydrostatic testing goal?
Select a reverse alloy assay to estimate unknown silver or gold fineness from water displacement, or compare against a reference coin standard.
Select Target Coin or Alloy Standard
Tap a reference world coin below to load its theoretical specific gravity (g/cm³) and expected water displacement.
Calibrate Hydrostatic Assay Parameters
Confirm your alloying base metal, target benchmark density, and water temperature before entering your scale readings.
Enter Dry & Submerged Scale Readings
Genuine Coin Alloys vs. Counterfeit Metal Density Chart
Compare the specific gravity (g/cm³) of authentic monetary silver and gold alloys against common counterfeit base metals such as zinc, brass, cupronickel, lead-tin pewter, and gold-plated tungsten.
| Alloy / Metal Standard | Composition or Counterfeit Signature | Classification | Specific Gravity & Action |
|---|---|---|---|
| .999 Fine Silver (Bullion) | 99.9% Pure Silver | Genuine Mint Alloy |
10.49 g/cm³
|
| .925 Sterling Silver | 92.5% Silver, 7.5% Copper | Genuine Mint Alloy |
10.40 g/cm³
|
| .900 Standard Coin Silver | 90% Silver, 10% Copper | Genuine Mint Alloy |
10.34 g/cm³
|
| .835 Continental LMU Silver | 83.5% Silver, 16.5% Copper | Genuine Mint Alloy |
10.22 g/cm³
|
| .833 Thaler Silver | 83.3% Silver, 16.7% Copper | Genuine Mint Alloy |
10.19 g/cm³
|
| .800 World Circulation Silver | 80% Silver, 20% Copper | Genuine Mint Alloy |
10.15 g/cm³
|
| .750 Commonwealth & Philippine Silver | 75% Silver, 25% Copper | Genuine Mint Alloy |
10.08 g/cm³
|
| .720 Dutch & Mexican Silver | 72% Silver, 28% Copper | Genuine Mint Alloy |
10.02 g/cm³
|
| .500 Half-Silver Alloy | 50% Silver, 50% Cu-Ni-Zn | Genuine Mint Alloy |
9.65 g/cm³
|
| .9999 Fine Gold (24 Karat) | 99.99% Pure Gold | Genuine Mint Alloy |
19.32 g/cm³
|
| .986 Ducat Gold (23.6 Karat) | 98.6% Gold, 1.4% Copper | Genuine Mint Alloy |
18.85 g/cm³
|
| .917 Crown Gold (22 Karat) | 91.67% Gold, 8.33% Copper/Silver | Genuine Mint Alloy |
17.56 g/cm³
|
| .900 Monetary Gold (21.6 Karat) | 90% Gold, 10% Copper | Genuine Mint Alloy |
17.16 g/cm³
|
| Bi-Metallic: CuNi Ring / Brass Core | CuNi Outer Ring + 3-Layer Nickel-Brass Core (e.g. 2 Euro, £1) | Genuine Mint Alloy |
8.65 g/cm³
|
| Bi-Metallic: Brass Ring / CuNi Core | Nickel-Brass Outer Ring + CuNi Core (e.g. 1 Euro) | Genuine Mint Alloy |
8.70 g/cm³
|
| Nordic Gold (Cu89 Al5 Zn5 Sn1) | 89% Cu, 5% Al, 5% Zn, 1% Sn | Genuine Mint Alloy |
7.85 g/cm³
|
| Cupronickel Clad Copper | 91.67% Copper, 8.33% Nickel | Genuine Mint Alloy |
8.92 g/cm³
|
| Standard Cupronickel (75% Cu, 25% Ni) | 75% Copper, 25% Nickel | Genuine Mint Alloy |
8.94 g/cm³
|
| Classic Coinage Bronze (95% Cu) | 95% Copper, 5% Tin/Zinc | Genuine Mint Alloy |
8.80 g/cm³
|
| Nickel Silver / CuNiZn (Cu70 Zn18 Ni12) | 70% Copper, 18% Zinc, 12% Nickel | Genuine Mint Alloy |
8.70 g/cm³
|
| Magnetic Nickel-Plated Steel (NGC) | 94% Steel Core, 6% Nickel Plating (Magnetic) | Genuine Mint Alloy |
7.87 g/cm³
|
| Zinc / Die-Cast White Metal Alloy | Low-cost cast counterfeits of silver crowns and dollars | Counterfeit Core | 7.14 g/cm³ |
| Silver-Plated Carbon Steel / Iron | Magnetic counterfeits common in fake trade dollars and 2 Euro coins | Counterfeit Core | 7.85 g/cm³ |
| Yellow Brass / Tombac Alloy | Used to imitate gold sovereigns and 20 Francs gold pieces | Counterfeit Core | 8.52 g/cm³ |
| Copper-Nickel (Cupronickel 75/25) | Most common non-magnetic base metal used in fake silver coins | Counterfeit Core | 8.92 g/cm³ |
| Lead-Tin Pewter Core | Heavy, soft core used to fake worn silver or thick gold coins | Counterfeit Core | 11.34 g/cm³ |
| Gold-Plated Tungsten (Wolfram) Core | High-density core matching pure 24k gold (requires caliper check on 22k coins) | Counterfeit Core | 19.25 g/cm³ |
Frequently Asked Questions About Coin Specific Gravity Testing
1. Weigh the dry coin on a 0.01 g digital scale (Wair). 2. Place a lightweight plastic cup filled with distilled water on the scale and press Tare (Zero). 3. Suspend the coin in a loop of fine nylon thread or dental floss so it is completely submerged in the center of the water without touching the bottom or sides, and tap off any air bubbles. 4. Record the displayed water displacement weight (Wdisp) and enter both numbers above.
Enter Your Water ReadingsIn a binary monetary alloy (such as silver alloyed with copper, or gold alloyed with copper), the inverse density of the coin equals the mass-weighted sum of the inverse densities of its two constituent metals. Because pure silver (10.49 g/cm³) and pure gold (19.32 g/cm³) have significantly higher densities than copper (8.96 g/cm³), our engine solves the harmonic density equation to estimate the exact millesimal fineness.
Value Your Assayed CoinPure tungsten (19.25 g/cm³) closely matches pure 24-karat .9999 gold (19.32 g/cm³). However, classic 21.6k (.900) and 22k (.917) gold coins—such as Krugerrands, Sovereigns, and US Double Eagles—have a lower specific gravity (17.16 to 17.56 g/cm³). A tungsten core inside a 22k coin will either register too dense in water or require an oversized thickness that our Caliper Volume Check flags immediately.
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