Half-life is the time it takes for half of a radioactive substance to decay. After 1 half-life: 50% remains. After 2: 25%. After 10: ~0.1%. Each element has a unique half-life.

What is carbon-14 half-life?

Carbon-14 has a half-life of 5,730 years. This allows radiocarbon dating to determine the age of organic materials up to about 50,000 years old.

Half-Life Calculator

Quick answer: Enter initial amount, half-life period, and time to calculate remaining and decayed amounts.

Calculate radioactive decay using the half-life formula: N = N₀ × (0.5)^(t/t½). Enter initial amount, half-life, and time elapsed to find how much substance remains.

Last reviewed: April 2026Report an error

Initial Amount (units)

Half-Life (years)

Time Elapsed (years)

Remaining

25.0000

25.0000 units remaining (25.00%) after 2.00 half-lives.

Remaining

25.0000

Decayed

75.0000

% Remaining

25.00%

Number of Half-lives

2.00

How to Use This Half-Life Calculator

1Enter the initial amount of the substance.
2Enter the half-life (in any time unit — just be consistent).
3Enter the time elapsed.
4Read remaining amount, decayed amount, and number of half-lives.

Frequently Asked Questions

: Half-life is the time it takes for half of a radioactive substance to decay. After 1 half-life: 50% remains. After 2: 25%. After 10: ~0.1%. Each element has a unique half-life.
: Carbon-14 has a half-life of 5,730 years. This allows radiocarbon dating to determine the age of organic materials up to about 50,000 years old.

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Half-Life Calculator

How to Use This Half-Life Calculator

Frequently Asked Questions

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