Half-Life Calculator
Calculate the half-life, initial quantity, or remaining quantity of a decaying substance. Perfect for physics, chemistry, and understanding radioactive decay.
Math Tools·Physics
Half-Life Calculator
Calculate decay variables. Results update as you type.
Calculate the remaining quantity of a substance after a certain time.
Starting amount
Time passed
Half-life of substance
Remaining Quantity
25
◒
Formula
100 × (1/2)^(10 ÷ 5) = 25Breakdown
Initial
100
Elapsed time
10
Half-life
5
Remaining
25
Quick Reference
- N₀Initial Quantity (amount before decay)
- N(t)Remaining Quantity (amount after time t)
- tElapsed Time
- t₁/₂Half-Life (time for quantity to halve)
Common Formulas
- Remaining:
N(t) = N₀ × (1/2)^(t / t₁/₂) - Initial:
N₀ = N(t) / (1/2)^(t / t₁/₂) - Time:
t = −t₁/₂ × ln(N(t)/N₀) / ln(2) - Half-Life:
t₁/₂ = −t × ln(2) / ln(N(t)/N₀)