Enter your carbon-14 measurement — as fraction remaining (F), percent modern carbon (pMC), or activity ratio (A/A₀) — choose your preferred half-life, and this Radiocarbon Dating Calculator gives you the sample age in years BP, decay constant (λ), percent remaining, and an estimated calendar year.
Sample Age
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Fraction Remaining
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Percent Remaining
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Decay Constant (λ)
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Estimated Calendar Year
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Carbon dating is a method of determining the age of organic materials by measuring the decay of Carbon-14, a radioactive isotope. Living organisms maintain a constant ratio of C-14 to C-12 by exchanging carbon with the atmosphere, but when they die, the C-14 begins to decay with a half-life of 5,730 years.
Carbon dating is generally accurate for samples up to about 50,000 years old. The accuracy depends on factors like contamination, calibration curves, and laboratory techniques. Modern methods can achieve precision within ±30-80 years for well-preserved samples.
Years BP stands for 'years Before Present,' with 'Present' defined as 1950 CE. This standardized reference point accounts for the fact that atmospheric C-14 levels have changed over time, particularly due to nuclear testing after 1950.
Carbon dating is effective for samples between about 500 and 50,000 years old. Beyond 50,000 years, so little C-14 remains that measurements become unreliable. For older samples, other radiometric dating methods are used.
Fraction remaining (F) is the ratio of current C-14 to the original amount (0-1), while percent modern carbon (pMC) expresses this as a percentage (0-100%). They're related: pMC = F × 100%.
The original half-life determined by Libby was 5,568 years, but more accurate measurements later established 5,730 years as the correct value. Some laboratories still use the old value for consistency with historical data.
Carbon dating works on organic materials that were once alive, such as wood, charcoal, bone, shells, peat, and textiles. Inorganic materials like rocks and metals cannot be carbon dated directly.
All measurements relate to the fraction of C-14 remaining: Fraction (F) = pMC/100 = Activity ratio (A/A₀). Age is calculated using the decay equation: t = -ln(F)/λ, where λ is the decay constant.