Half-Life Calculator
Remaining and decayed amount over time given a half-life.
How it works
Remaining = initial × (1/2)^(time ÷ half-life)
Each half-life halves the amount: 2 half-lives leave 1/4, 3 leave 1/8.
Worked example
Start 100 mg, half-life 6 hours, after 24 hours:
Four half-lives pass: remaining = 100 × (1/2)⁴ = 6.25 mg.
Notes and limitations
Formula: N = N₀ × (1/2)^(t/T). Half-life is statistical; individual decay is unpredictable. Drug half-lives also depend on liver and kidney function.