# Half-Life Calculator

> Calculate radioactive decay, half-life, or remaining quantity.

Page: https://askcalculators.com/calculator/half-life-calculator/
Definition: https://askcalculators.com/calculator/half-life-calculator/definition.json
JSON Schema: https://askcalculators.com/calculator/half-life-calculator/schema.json
Version: 7.0.0
Maintained by: AskCalculators (software project; not a credentialed reviewer)
Qualified review: pending. Automated checks do not establish professional approval.
Page status: Live
Review status: Pending

## Use
Open the calculator page and enter values. Query-string parameters can restore and bookmark a calculation.
Example: https://askcalculators.com/calculator/half-life-calculator/?initial=100&time=10&remaining=50&mode=find-remaining

## Inputs
- initial: Initial Quantity (N₀); type=number; optional; default=100
- halfLife: Half-Life (t½); type=number; optional; default=
- time: Elapsed Time (t); type=number; optional; default=10
- remaining: Remaining Quantity (Nₜ); type=number; optional; default=50
- mode: Mode; type=select; optional; default=find-remaining

## Outputs
- result: Result; format=text; primary

## Formula
Remaining amount = initial amount × (1/2)^(elapsed time ÷ half-life).

## Rules
- Empty optional inputs are undefined, not zero.
- Hidden conditional inputs are ignored.
- Do not invent missing required inputs.