Half-Life Calculator: Radioactive Decay and Rema...
Calculate the remaining quantity of a radioactive substance after any number of half-lives. Learn the decay law, decay constant, and their applications in nuclear...
What is Half-Life?
Half-life (t₁/₂) is the time required for half of a radioactive substance to decay. It is characteristic of each radioisotope and ranges from fractions of a second (radon-213: 0.0016 ms) to billions of years (uranium-238: 4.5 Gy). Radioactive decay is the basis of carbon dating, nuclear medicine, and reactor safety.
☢️ Half-Life Calculator
Use our free calculator for instant, accurate results.
📐 Formula
N(t) = N₀ × (½)^(t/t½)
N₀ = initial quantity, t = elapsed time, t½ = half-life. Equivalently: N(t) = N₀ × e^(−λt) where λ = ln(2)/t½ is the decay constant.
📝 Worked Example
Carbon-14 half-life = 5730 years. A sample initially has 1000 atoms. After 11,460 years (2 half-lives):
N = 1000 × (½)² = 1000/4 = 250 atoms remaining
📝 How to Use the Calculator
❓ FAQ
What is radioactive activity?
Activity (A) is the number of decays per second. A = λN, measured in Becquerels (Bq) or Curies (Ci). 1 Ci = 3.7×10¹⁰ Bq.
How is carbon dating done?
All living organisms absorb C-14 from the atmosphere. After death, C-14 decays without replenishment. Comparing current C-14 to expected gives the age.
Veer Kumavat
Founder & AuthorVeer is a 14-year-old student from Nashik, Maharashtra, who built SciFi Calculators to help students worldwide master STEM subjects. He is passionate about making complex science and math problems accessible through intuitive digital tools.