Carbon-14 Dating Calculator
Estimate the age of a sample from its remaining carbon-14 fraction (or activity), using the 5,730-year half-life — or predict the fraction left after a given age.
How it works
t = −(T½ ÷ ln 2) · ln(N/N₀) · N/N₀ = e^(−λt), λ = ln 2 ÷ T½
Living things constantly exchange carbon with the atmosphere, so their C-14 matches it; at death intake stops and the isotope decays with a 5,730-year half-life. Measuring the surviving fraction gives an elapsed time. Labs report a “conventional radiocarbon age” using Libby’s older 5,568-year value and then calibrate against tree rings and corals, because atmospheric C-14 has varied over time.
Worked example
25% remaining = two half-lives → 2 × 5,730 = 11,460 years.
Frequently asked questions
Why is there a 50,000-year limit?
After nine half-lives less than 0.2% remains, and contamination or background swamps the signal.
What is “calibrated age”?
The raw radiocarbon age corrected for past changes in atmospheric C-14 using the IntCal curve; it can differ by centuries.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.