How this calculator works
Compare sample carbon-14 activity or isotope ratio with its initial value. The simple exponential model assumes a closed sample and uses 5730 years by default. This gives an uncalibrated decay age; archaeological calendar ages need atmospheric calibration, fractionation and reservoir corrections. Conventional radiocarbon ages use the historical 5568-year Libby half-life, so change the input when reproducing that convention.
Formula
t = -T ln(f)/ln(2); f = 2^(-t/T), where f is the remaining fraction.
Worked example
At 50% remaining and T = 5730 years, t = 5730 years. At 25%, t = 11460 years.
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Frequently asked questions
Can the remaining fraction be zero?
No finite age corresponds to exactly zero remaining carbon-14.
Is this a calibrated calendar date?
No. A calibration curve and sample-specific corrections are required.
Can I date a rock with this?
Carbon-14 dating applies to suitable carbon-bearing material, usually material that exchanged carbon while alive.