Use this numismatic calculation to document a collection, metal content, historical denomination, minting error, grading cost, auction price, or market scenario with explicit measurements and prices.

First Diameter Millimeters (mm)

Required number input.

Second Diameter Millimeters (mm)

Required number input.

Third Diameter Millimeters (mm)

Required number input.

Average three diameter measurements at different orientations. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Average Diameter Millimeters (mm)

The resulting average diameter millimeters returned as a number.

• Coin value and attribution depend on authenticity, date, mint, variety, grade, surfaces, provenance, market liquidity, fees, metal assay, and current spot prices. Images and arithmetic cannot replace expert authentication or in-hand grading.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Retain weight, diameter, photographs, references, transaction fees, and price dates; verify valuable pieces with recognized catalogues and qualified independent experts.

• Planchet Thickness Average

  Average three caliper measurements around a planchet; local rim or relief features can distort readings.

• Average Cost Basis Calculator

  Average a lot's acquisition cost over its coins; individual coins may have different actual bases.

• Appraisal Average Value Per Item

  Average the stated appraised value across collection items.