Carbon-14 has a half-life of 5,730 years. This means that after 5,730 years, only half of the original amount of Carbon-14 remains in a sample of organic material. After an additional 5,730 years, only a quarter of the original amount remains, and so on. The amount of Carbon-14 remaining is used to determine the age of organic materials. After about 50,000-60,000 years (or approximately nine half-lives), the amount of Carbon-14 remaining is generally too small to measure reliably.