How to use the half-life from measurements calculator
Find half-life from two measurements of a decaying sample. Enter initial amount, amount after time t, elapsed time in the fields above; the half-life, decay constant are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- N0 β Initial amount
- N β Amount after time t
- t β Elapsed time (days)
Worked example
With initial amount = 1000, amount after time t = 250, elapsed time = 16 days, the calculator gives half-life β 8 days; decay constant β 0.0866434 1/day.
Frequently asked questions
What is the formula for the half-life from measurements calculation?
Half-life (days) = t Γ ln(2) / ln(N0 / N). Decay constant (1/day) = ln(N0 / N) / t. Here N0 is initial amount, N is amount after time t, t is elapsed time (days).
What inputs do I need for the half-life from measurements calculator?
You need initial amount, amount after time t, elapsed time in days. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.