How much does my coin weigh? This is a common question first asked when a coin seems not quite right. Is it an error coin? Is the coin missing design or a part of the coin? Does it feel lightweight or too heavy? Does it sound different when dropped on the bench? Does the metal it’s made from appear different to normal? A coins weight must be accurately measured on a scale ideally to 2 decimal places. This is usually done a jewellers scale.
A coin has a legal parameter that it fits with regard to weight. A normal weight can differ up or down and still fit into the tolerance for a genuine coin. It can be handy to know these allowable tolerances as we examine coins closely. This is why we’ve compiled this handy guide to help collectors out. Information derived from Australian Currency Determinations for legal currency.
Decimal Coin Tolerances
| Coin | Standard Design | Metal Composition | Shape | Edge | Diameter (max) mm | Thickness (max) mm | Weight grams | Weight Tolerance grams | Weight Minimum grams | Weight Maximum grams |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 Cent (1c) | Feather Tailed Glider | 97% Copper, 2.5% Zinc , .5% Tin | Round | Plain | 17.75 | 1.80 | 2.60 | +/- 0.3 | 2.30 | 2.90 |
| 2 Cent (2c) | Frill-Necked Lizard | 97% Copper, 2.5% Zinc , .5% Tin | Round | Plain | 21.80 | 2.20 | 5.20 | +/- 0.3 | 4.90 | 5.50 |
| 5 Cent (5c) | Echidna | 75% Copper, 25% Nickel | Round | Milled | 19.53 | 1.90 | 2.83 | +/- 0.33 | 2.50 | 3.16 |
| 10 Cent (10c) | Lyrebird | 75% Copper, 25% Nickel | Round | Milled | 23.82 | 2.30 | 5.65 | +/- 0.49 | 5.16 | 6.14 |
| 20 Cent (20c) | Platypus | 75% Copper, 25% Nickel | Round | Milled | 28.65 | 2.92 | 11.30 | +/- 0.78 | 10.52 | 12.08 |
| 50 Cent (50c) | Coat of Arms | 75% Copper, 25% Nickel | Dodecagon (12 sided) | Plain | 31.65 | 3.16 | 15.55 | +/- 0.96 | 14.59 | 16.51 |
| One Dollar ($1) | Mob of Kangaroos | 92% Copper, 6% Aluminium, 2% Nickel | Round | Interupted Milled | 25.20 | 3.46 | 9.00 | +/- 0.66 | 8.34 | 9.66 |
| Two Dollar ($2) | Aboriginal Elder | 92% Copper, 6% Aluminium, 2% Nickel | Round | Interupted Milled | 20.62 | 3.70 | 6.60 | +/- 0.6 | 6.00 | 6.60 |
