Half-Life 10 — How Much Remains After 20 Periods?
With a half-life of 10 periods and 20 periods elapsed (two half-lives), exactly 25% of the original amount remains.
How to use this tool
- Enter initial amount, half-life (time units) and elapsed time (same units) in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your remaining amount and the full breakdown beneath it.
After exactly two half-lives (20 periods), one quarter of the original 1,000 remains — 250 units.
Frequently asked questions
- What substances have known half-lives?
- Carbon-14 has a half-life of about 5,730 years (used in carbon dating). Uranium-238 has ~4.5 billion years. Iodine-131 used in medicine has ~8 days.
- Can I use this for non-radioactive decay?
- Yes — any process that halves on a fixed schedule (drug concentration, population loss, etc.) can be modelled this way.