Half-Life Calculator

Calculate radioactive decay, half-life, and carbon dating

Calculate Remaining Amount
Calculate Time Elapsed
Calculate Half-Life
Common Radioactive Isotopes
Isotope Half-Life Decay Type Common Use Action
Formulas
Decay Formula
N(t) = N₀ × (½)^(t/t½)
or N(t) = N₀ × e^(-λt)
Where:
  • N(t) = Amount remaining
  • N₀ = Initial amount
  • t = Time elapsed
  • = Half-life
  • λ = Decay constant = ln(2)/t½
Key Facts
  • After 1 half-life: 50% remains
  • After 2 half-lives: 25% remains
  • After 3 half-lives: 12.5% remains
  • After 10 half-lives: ~0.1% remains
Quick Examples

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Support This Free Tool

Every coffee helps keep the servers running. Every book sale funds the next tool I'm dreaming up. You're not just supporting a site — you're helping me build what developers actually need.

500K+ users
200+ tools
100% private
Privacy Guarantee: Private keys you enter or generate are never stored on our servers. All tools are served over HTTPS.