The charred wood of an ancient campfire still whispers its age — every living thing carries a radioactive clock that starts ticking at death. In plain words, isotopes are atoms of the same element with different neutron counts, and unstable ones decay at a fixed rate described by the half-life: the time for half the atoms to transform. Carbon-14's half-life is 5,730 years, so a sample holding half the carbon-14 of fresh wood died about 5,730 years ago. Archaeologists date artifacts, doctors trace thyroid function with iodine-131, and nuclear engineers manage reactor fuel — all by reading these clocks. The math is exponential: each half-life multiplies the remainder by one half, relentlessly.

This calculator applies the half-life decay. Type the number of half-lives elapsed into the Variable A box, say 1 — Variable B accepts a second value for comparison. Read the remaining fraction from the Result box: 0.5 after one half-life. Try 2 to see a quarter remain, and remember that the fraction never truly reaches zero, it just keeps halving.

With the pre-filled defaults — Variable A 10, Variable B 5 — the Isotope Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.