What is the half-life of Carbon-14?

Carbon-14 has a half-life of 5,730 years. This limits carbon dating to samples no older than about 50,000 years, after which so little C-14 remains that measurement becomes unreliable.

Why does the K-Ar system require a different input?

Potassium-Argon dating measures the ratio of radiogenic Argon-40 to remaining Potassium-40. Because argon is a gas that escapes when rock melts, the clock resets at each volcanic event, making K-Ar ideal for dating igneous rocks.

What does "daughter-to-parent ratio" mean?

It is the ratio of accumulated stable daughter isotope (e.g., Pb-206) to remaining radioactive parent isotope (e.g., U-238). A higher ratio indicates an older sample.

How accurate is radiometric dating?

When done properly with precise mass spectrometry, radiometric dating is accurate to within 0.1–1% of the true age. Accuracy depends on the system chosen, sample purity, and whether the sample remained a closed system since formation.

Can I date any material with Carbon-14?

Only materials that were once living (organic matter) or that exchanged carbon with the atmosphere can be dated with C-14. Rocks and minerals do not contain carbon-14 and require other isotope systems.

What is the decay constant (lambda)?

The decay constant is the probability per unit time that a given atom will decay. It is related to the half-life by lambda = ln(2) / half-life. Each isotope has a unique, experimentally determined decay constant.

Radiometric Dating Calculator

Select an isotope system, enter measured ratios or percentages, and get the calculated age of your sample in years.

Isotope System

Select Isotope System

C-14 Remaining (%)

Enter a value between 0 and 100

Enter a value and click Calculate Age

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Summary

Radiometric dating determines the age of a rock or organic sample by measuring the ratio of a radioactive parent isotope to its stable daughter product. Each isotope system has a known decay constant (lambda), which relates the current ratio to elapsed time via the equation t = ln(N0/N) / lambda. This tool supports four widely used systems: Carbon-14 (up to ~50,000 years), Potassium-Argon (thousands to billions of years), Uranium-Lead (millions to billions of years), and Rubidium-Strontium (billions of years).

How it works

Select the isotope system that matches your sample type and age range.
Enter the measured value — either the percentage of parent isotope remaining, or the daughter-to-parent ratio.
The calculator applies the decay equation t = ln(1 + D/P) / lambda (or t = −ln(N/N0) / lambda for C-14).
The calculated age is displayed in years, with scientific notation for very large values.
Adjust your input to explore how measurement uncertainty affects the age estimate.

Use cases

Estimate the age of organic material using Carbon-14 remaining percentage.
Date volcanic rocks and lava flows with Potassium-Argon ratios.
Determine the age of ancient zircon crystals using Uranium-Lead ratios.
Date metamorphic and igneous rocks with the Rubidium-Strontium system.
Cross-check ages from different isotope systems for consistency.
Use in geology, archaeology, and geophysics coursework or research.
Explore the sensitivity of age estimates to measurement precision.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu