Use this geological calculation for a transparent first-pass interpretation of measured rock, soil, fluid, well, stratigraphic, isotopic, geophysical, or seismic data under an explicitly selected model.

206Pb/238U

Radiogenic 206Pb/238U ratio.

207Pb/235U

Radiogenic 207Pb/235U ratio.

Convert 206Pb/238U and 207Pb/235U ratios into concordia-style ages in Ma and their percent discordance. 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]

206Pb/238U age

Age from the 206Pb/238U ratio in Ma.

207Pb/235U age

Age from the 207Pb/235U ratio in Ma.

Discordance

Percent discordance, 100*(t207-t206)/t207; zero means concordant.

• Radiometric ages require the correct decay constants, isotopic ratios, standards, common-component correction, closure interpretation, initial composition, and analytical uncertainties. Disturbance, inheritance, diffusion, alteration, and model choice can make a calculated number differ from the geological event age.
• 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.

Compare independent measurements and models, retain units and analytical metadata, propagate uncertainty, and validate interpretations against logs, cores, maps, laboratory data, or field observations.

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