Radiochemical Dating Calculator

Work out radiochemical dating instantly with clear inputs, formula shown and shareable results.

About Radiochemical Dating Calculator

Radioactive decay is first order, so the age follows from the surviving fraction: t = ln(1/f) divided by the decay constant, and the decay constant is ln2 over the half-life. A carbon-14 sample at 25% of its original activity has run two half-lives, so it is about 11,460 years old.

Formulas

Decay constant

lambda = ln2 / half-life

Age

t = ln(N0/N) / lambda = half-life x log2(N0/N)

Worked example

With the default values below, Radiochemical Dating Calculator returns Age Of The Sample of 11,460.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Half-life of the isotopeminimum 0 years: 5,730 years
Fraction of the isotope still presentaccepts 0–1: 0.25

Results

Age Of The Sample: 11,460.0 years
Decay Constant: 1.2097 × 10⁻⁴ 1/year
Half-Lives Elapsed: 2.000
Isotope Remaining: 25.000%

Step by step

1Values used
2Decay constant
3Age
4Age Of The Sample= 11,460.0 years
5Decay Constant= 0.0001 1/year
6Half-Lives Elapsed= 2.000
7Isotope Remaining= 25.000

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How much carbon-14 is left after two half-lives?

One quarter. Each half-life halves what remains, so 100 g becomes 50 g then 25 g.

Why does carbon dating stop working past about 50,000 years?

After roughly nine half-lives under 0.2% remains, which is too little to measure reliably against background.