Radiocarbon Dating Calculator
Pair measured sample activity with modern standards to compute ages based on exponential radioactive decay.
Use counts per minute, Bq, or percent modern carbon.
Default uses Carbon-14 half-life 5730 years.
Decay constant
0.000121 1/years
Fraction modern
0.25
Sample age
11,460 years
How to Use This Calculator
Measure modern reference
Use modern carbon standards or living tissue to establish baseline activity A0.
Measure sample activity
Determine the activity of the archaeological or geological sample, adjusting for background counts.
Confirm half-life
Use 5730 years for Carbon-14 or substitute a different half-life for other isotopes.
Review computed age
The calculator reports the sample age along with the decay constant and fraction modern carbon.
Formula
t = (1/lambda) * ln(A0 / As)
lambda = ln(2) / t1/2. A0 is modern activity, As sample activity. Age is reported in the same time units used for the half-life.
Example
With A0 = 100 counts per minute, As = 25, and t1/2 = 5730 years: lambda = 1.21e-4 1/years, age = ln(100/25) / lambda about 11460 years.
Full Description
Radiocarbon dating leverages the predictable decay of Carbon-14 to Nitrogen-14, comparing sample activity to modern references to estimate age.
Corrections such as reservoir effects and isotopic fractionation may be needed for high precision studies, but the basic exponential decay model provides a first estimate.
Frequently Asked Questions
Can I input percent modern carbon?
Yes. Set A0 to 100 and use the sample percent as As.
What if the sample activity is zero?
Zero implies the sample is beyond the measurable range. Report age as greater than the detection limit.
Does background radiation matter?
Subtract instrument background from both sample and reference measurements before entering values.
Can I change the half-life?
Yes. Enter any half-life to model other isotopes or updated Carbon-14 values.
How do reservoir corrections apply?
Apply correction factors to As prior to using the calculator to account for marine or old carbon reservoirs.