half life calculator
Free calculate half-life for radioactive decay, chemical reactions, and first-order kinetics using decay constant.
Enter Decay Data
Rate constant for first-order decay
Time elapsed since initial amount
Results
Enter decay data to calculate half-life
Half-Life Formulas
Half-Life Formula
t₁/₂ = ln(2) / λ
- • t₁/₂ = Half-life
- • λ = Decay constant
- • ln(2) ≈ 0.693
- • First-order kinetics
- • Independent of initial amount
Decay Equation
N(t) = N₀ × e^(-λt)
- • N(t) = Amount at time t
- • N₀ = Initial amount
- • λ = Decay constant
- • t = Time elapsed
- • Exponential decay