How carbon 14 dating is done?
The process is as described below.
Carbon-14 dating is used for (i) carbon-14 decays slowly in a living organism to nitrogen (half life 5730 years) (ii) amount of carbon-14 lost is continually replenished as long as the organism takes in air or food (however, once the organism dies, it ceases to absorb carbon-14).
Hence, it is a good way of determining the age of certain archaeological artifacts of biological origin (could be bone, fiber, wood, plant remnants etc.) up to about 50,000 years old.
If a fossil has say 25% of carbon-14 as compared to living sample than it is 11460 years old (as it has one-fourth carbon it is 5730*2=11460 years old).
General formula for time