Radiocarbon Dating Calculator

Frequently Asked Questions

What is the half-life of carbon-14?

Carbon-14 has a half-life of 5730 years, meaning half of it decays over that period. This calculator uses that value to estimate sample age from the fraction of carbon-14 remaining.

How far back can radiocarbon dating reach?

It is generally reliable up to about 50,000 years. Beyond that, too little carbon-14 remains to measure accurately even with modern accelerator mass spectrometry, and trace contamination with recent carbon can produce significant errors.

Why do lab results differ from this calculator?

Laboratory radiocarbon dates are calibrated against tree-ring records and marine sediment data to correct for historical variation in atmospheric carbon-14 levels. This calculator uses the raw decay formula without calibration, so it gives an uncalibrated estimate that may differ from an official calibrated date by decades to centuries for older samples.

Can radiocarbon dating be used on any material?

No. It works only on organic materials that were once alive, such as bone, wood, charcoal, shell, and fabric. It cannot directly date pottery, stone, metal, or geological formations unless those materials contain trapped organic carbon.

Provided by AllCalculators.io
Free online calculators for everyday. No registration required.

Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

JavaScript is required to use the interactive calculator above. The questions and answers below remain readable without JavaScript.

How This Calculator Works

Radiocarbon dating estimates the age of organic material by measuring how much of its carbon-14 has decayed. Living organisms continuously absorb carbon-14 from the atmosphere through respiration and feeding. Once an organism dies, it stops exchanging carbon with the environment, and the carbon-14 already present begins decaying at a steady, predictable rate. That constant decay rate acts like a built-in clock that scientists can read by measuring the fraction of carbon-14 remaining compared to stable carbon-12.

The Formula

The age equals the natural logarithm of the fraction of carbon-14 remaining divided by the natural logarithm of one half, then multiplied by the half-life of 5730 years. When exactly half the original carbon-14 is left, the equation returns one half-life, or 5730 years. When one quarter remains, the result is two half-lives, or 11460 years. Each additional half-life reduces the remaining fraction by half again.

Reading The Result

The estimated age is given in years before the present, with a rounded figure that reflects the inherent uncertainty of the method. Radiocarbon dating is generally reliable for organic samples up to about 50,000 years old. Beyond that, too little carbon-14 remains to measure accurately, and contamination from even small amounts of modern carbon can skew results significantly.

Tips

The carbon-14 half-life used here is 5730 years, the currently accepted value.

Enter the percent of original carbon-14 still present in the sample.

Real laboratory dates are calibrated against tree-ring chronologies (dendrochronology) to account for historical variation in atmospheric carbon-14 levels.

Where Carbon-14 Comes From

Carbon-14 is continuously produced in the upper atmosphere when cosmic ray neutrons collide with nitrogen-14 atoms. The resulting carbon-14 combines with oxygen to form carbon dioxide, which circulates through the atmosphere and is absorbed by plants during photosynthesis. Animals absorb it by eating plants or other animals. This process maintains a roughly constant ratio of carbon-14 to carbon-12 in living organisms, though the atmospheric ratio has varied slightly over millennia, which is why laboratory dates are calibrated against known-age tree rings and other records.

Limitations of Radiocarbon Dating

Radiocarbon dating works only on organic materials: bone, wood, charcoal, shell, peat, and similar carbon-containing substances. It cannot date rocks, pottery, or metal directly. The method is most accurate for samples younger than about 30,000 years and becomes unreliable beyond 50,000 years. Contamination with modern carbon drastically reduces apparent age, while contamination with ancient carbon increases it. The Suess effect, caused by industrial burning of fossil fuels releasing old carbon into the atmosphere, and nuclear bomb testing in the 1950s and 1960s, which spiked atmospheric carbon-14, both affect calibration curves for recent samples.

When to Use Other Dating Methods

For samples older than 50,000 years, other radiometric methods are necessary. Potassium-argon dating works for volcanic rocks up to billions of years old. Uranium-lead dating is used for zircon crystals in ancient rocks and can reach the age of the solar system. Thermoluminescence and optically stimulated luminescence date the last time minerals were exposed to heat or sunlight, which is useful for pottery and sediment layers that contain no organic material. Each method has a different applicable time range and material requirement, so choosing the right technique depends on the sample type and age estimate needed.

Radiocarbon Dating Calculator

Frequently Asked Questions

Related Science Calculators