Half-Life Calculator

Calculate radioactive decay: remaining amount, half-life, decay constant, or time elapsed.

☢️ Half-Life Calculator

N₀ – Initial Amount any unit (g, mol, Bq…)

t½ – Half-Life time unit

t – Time Elapsed same time unit

N – Remaining Amount same unit as N₀

⚠ Enter valid positive values for the three known variables.

Decay Formula

N = N₀ × (½)^(t/t½)

Remaining Amount

—

units

☢️ Radioactive Decay Formula

N(t) = N₀ × (½)^(t/t½)

λ = ln(2) / t½ | t½ = ln(2) / λ

N(t) = amount remaining at time t
N₀ = initial amount
t½ = half-life (time for 50% to decay)
λ = decay constant

📖 Example – Carbon-14 Dating

✅ Archaeological Sample

C-14 half-life = 5730 years. Sample has 25% of original C-14. Find age.

N/N₀ = 0.25 = (½)^(t/5730)

t = 5730 × log₂(1/0.25) = 5730 × 2 = 11,460 years

❓ FAQ

What is half-life?

Half-life is the time required for half of a radioactive substance to decay. After 1 half-life: 50% remains, after 2: 25%, after 10: ~0.1%.

Does half-life apply to non-radioactive reactions?

Yes! First-order chemical reactions also have half-lives. The concentration halves every t½ regardless of initial concentration.

🔗 Related

Comprehensive Guide

Mastering Half-Life Calculations

Our free Half-Life Calculator simplifies complex chemistry mathematics, providing step-by-step clarity for analytical problem solving. Whether you're prepping for an AP Chemistry exam or working in a research lab, computing Half-Life quickly prevents cascading mathematical errors. Mastering the concepts behind Half-Life is crucial for understanding advanced chemical reactions and laboratory procedures.

Why is Half-Life Important?

In analytical chemistry, precision is everything. Having a reliable way to compute Half-Life saves time, prevents wasted materials, and ensures scientific accuracy.

⚡

Speed

Instant

🎯

Accuracy

100%

🎓

Level

All Levels

Always verify your input units before calculating. Mismatched units (e.g., using mL instead of L) are the most common source of error when determining Half-Life!

Common Applications

Academic Study: Speeding up repetitive calculations.
Laboratory Practice: Ensuring exact stoichiometry for reactions.
Data Validation: Studying for college-level chemistry tests.

Relying solely on the calculator without understanding the underlying formula. Always review the step-by-step breakdown to internalize the mechanics.