Carbon Dating Calculator
Sample age, half-lives elapsed, and range verdict from remaining carbon-14.
What it does
Radiocarbon dating reads the clock in dead carbon: living things match atmospheric carbon-14 until death, then the isotope decays with a 5,730 year half-life and nothing refreshes it. Half remaining means one half-life passed.
The tool above takes remaining carbon percent. It returns sample age with half-lives elapsed and a range verdict beside them.
The default of 50% gives 5,730 years and 1 half-life. A quarter gives 11,460 years and 2 half-lives, both inside the reliable window.
The method follows geological survey radiocarbon references with isotope program data matching each constant. Both set the half-life at 5,730 years with about a century to seventy millennia of reach.
How to use
- Enter remaining carbon-14 as percent of modern.
- Read age first for the headline years.
- Read half-lives for the decay count.
- Read the verdict before trusting old samples.
- Send real samples to labs for calibration curves.
Formula
- 5,730
- Carbon-14 half-life in years.
- log2
- Halvings counted from the remaining share.
- 100-70k
- Reliable dating window in years.
Simplified decay math without calibration curves, reservoir effects, or bomb carbon corrections that labs apply. Contamination bends young and old ends alike.
Worked example
Example: 50% modern carbon
Default: 50% remaining.
- Halvings: -log2(0.5) = 1 half-life.
- Age: 1 x 5,730 = 5,730 years.
- Window: inside 100 to 70,000 years.
- Quarter check: 25% would read 2 half-lives, 11,460 years.
- Tool shows 5,730 years, 1 half-life, Inside the reliable dating window.
Reference table
| Remaining | Age | Half-lives |
|---|---|---|
| 50% | 5,730 years | 1 half-life |
| 25% | 11,460 years | 2 half-lives |
| 12.5% | 17,190 years | 3 half-lives |
Limits
- Simplified math; labs calibrate against tree rings.
- Contamination ruins both ends of the range.
- Works on once living carbon only, never rock.
- Bomb carbon complicates post 1950 samples.
Common mistakes
- Dating inorganic rock with carbon methods.
- Ignoring calibration curves past raw years.
- Reading contamination as true age.
- Trusting results past 70,000 years.
- Forgetting 1950 is the modern baseline.
Try it yourself
Quick checks. Answers sit tucked under each question.
25% remaining?
2 half-lives: 11,460 years.
12.5% remaining?
3 half-lives: 17,190 years.
Over 100% entered?
Rejected: enter remaining carbon between 0 and 100%.
Questions
How does carbon dating work?
Dead carbon loses carbon-14 by halves every 5,730 years; the remainder dates death.
What is the half-life?
5,730 years for carbon-14.
How far back does it reach?
About 100 to 70,000 years reliably.
Why 1950 baseline?
Convention: modern means pre bomb 1950 atmospheric carbon activity.
Does it date rocks?
No. Only once living organic material; rocks need other isotopes.
Why do labs differ?
Calibration curves, reservoir corrections, and contamination handling refine raw years.