Half-Life Calculator

Calculate remaining quantity after radioactive decay using the half-life formula.

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Remaining

12.5000

Decayed87.5000
Num Halves3.00
Pct Remaining12.50 %
View formula & how it works →

Half-Life Formula

Formula

N(t) = N₀ × (1/2)^(t/t½)

Where:

  • N₀ = initial quantity
  • t = elapsed time
  • t½ = half-life

    • Properties

  • 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

    • Example Calculation

    100 units with a half-life of 5 after 15 time units.

    1. 01Number of half-lives = 15/5 = 3
    2. 02Remaining = 100 × (0.5)³
    3. 03= 100 × 0.125
    4. 04= 12.5

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