How Coin Weight Tolerances Work (And Why a Coin Might Be Slightly Off-Spec)

Short answer: mints publish not just a target weight but an acceptable tolerance range around it — a small, officially permitted variance reflecting the physical reality that no mechanical striking process produces every single coin at a perfectly identical weight. A coin within its published tolerance is completely normal and genuine; one meaningfully outside that range is worth investigating further.

Why Tolerances Exist At All

Striking millions of coins through a mechanical process inevitably produces tiny variances — in blank weight before striking, in metal flow during the strike itself, and in minor measurement precision. Official tolerance ranges acknowledge this physical reality rather than pretending every coin is identically, perfectly weighted to the milligram.

Typical Tolerance Ranges

Tolerances are generally quite tight — often within a fraction of a percent of the target weight for modern bullion coins — but the exact permitted range varies by mint and by coin. A mint's official specification sheet, where published, states both the target weight and the permitted tolerance, and this is the actual reference to check a coin against, not an assumption that every coin weighs exactly the stated figure.

When a Weight Discrepancy Is Normal

A coin weighing a very small amount above or below its stated target, within the published tolerance range, is completely normal and doesn't indicate anything wrong with the coin — this is expected manufacturing variance, not a defect or authenticity concern.

When It's a Red Flag

A coin weighing meaningfully outside its published tolerance — not a fraction of a percent, but a clearly noticeable discrepancy — is a legitimate reason for concern, potentially indicating a counterfeit, a genuine mint error (see our mint errors guide), or significant wear/damage affecting weight. The key distinction is whether the discrepancy falls within or clearly outside the officially stated tolerance.

How to Check

Weigh a coin on a scale precise enough to measure to at least 0.01 gram (a jeweler's or reloading scale, not a kitchen scale), and compare against both the target weight and published tolerance for that specific coin and size — not just a general "1 oz should weigh about 31 grams" assumption.

Summary

• Mints publish a target weight plus an acceptable tolerance range, not a single perfect figure every coin must hit exactly
• Small weight variance within the published tolerance is normal manufacturing reality, not a defect
• A discrepancy clearly outside the published tolerance is a legitimate authenticity or error concern
• Always check against the specific coin's own published spec and tolerance, not a general assumption