Choose a Preset or Enter Values
Select a known isotope like Carbon-14 or Uranium-238 from the presets, or manually enter your own initial and remaining amounts.
Half Life Calculator – Simple Decay Time Estimator
Solve for Half-Life, Remaining Amount, Time Elapsed, or Initial Amount Instantly.
Parameters
Result
--
Enter 3 values
Amount Decay
--%
Half-Lives
--
Decay Const (λ)
--
Decay Curve
Decay Steps Table
| Cycles | Time Elapsed | Amount Remaining |
|---|---|---|
| Calculate to generate step-by-step breakdown. | ||
How Half-Life Calculator Works
Enter any three known decay values and the calculator solves for the missing one — instantly, accurately, with a full breakdown.
Fill Exactly Three Fields
Input any three of the four variables — Initial Amount, Remaining Amount, Time Elapsed, or Half-Life — and leave the unknown blank.
Solve with One Click
Hit Calculate Solution and the engine applies the exponential decay formula instantly, solving for whichever variable you left empty.
Read the Decay Curve
A real-time decay graph renders automatically, plotting the entire decay curve and marking your calculated data point precisely.
Review the Step-by-Step Table
A decay steps table breaks down remaining amounts at each half-life interval, highlighting the row closest to your calculated time.
Export or Reset Anytime
Print your full decay report for lab work or coursework, or reset all fields with one click to run a completely new calculation.
Key Benefits of Half-Life Calculator
From nuclear physics students to medical professionals — discover why this tool is trusted for precise radioactive decay calculations.
Solves All 4 Decay Variables
Calculate half-life, initial amount, remaining amount, or time elapsed — fill three fields and the missing value is solved instantly.
Instant Real-Time Results
No waiting, no page reload — results, stats, decay curve, and step table all update the moment you click calculate.
Built-In Isotope Presets
Jump-start any calculation with preloaded isotopes — Carbon-14, Uranium-238, Iodine-131, Cesium-137, Plutonium-239 and more.
Live Exponential Decay Graph
A rendered decay curve visualizes your isotope's behavior over time with your calculated point marked precisely on the graph.
Decay Constant Calculated
The decay constant λ is computed automatically alongside your result — essential for advanced nuclear and physics coursework.
Half-Life Step-by-Step Table
A detailed breakdown shows remaining amounts at each half-life interval, with the closest matching row highlighted for reference.
Flexible Time Unit Support
Switch between seconds, minutes, hours, days, or years — handles any scale from short medical isotopes to geological timelines.
Print-Ready Report Output
Export a clean formatted print report of your decay calculation — ideal for lab submissions and academic assignments.
Who Should Use Half-Life Calculator
Whether you're studying nuclear decay, running lab simulations, or working in medicine — this calculator was built for your use case.
Students
Physics & Chemistry Students
Solve textbook decay problems, verify exam answers, and build intuition for exponential decay behavior across all science levels.
Researchers
Nuclear & Radiation Researchers
Quickly compute decay constants, remaining quantities, and time estimates for radioactive samples during experimental research.
Medical
Medical Physics Professionals
Calculate dosage decay for radiopharmaceuticals like Iodine-131 — ensuring accurate administration windows and safe patient planning.
Educators
Science Teachers & Educators
Demonstrate live decay calculations in the classroom, generate visual decay curves, and produce tables for student learning materials.
Geologists
Geologists & Archaeologists
Use Carbon-14 and Uranium-238 presets to estimate the age of geological formations, fossils, and ancient artifacts with precision.
Safety
Radiation Safety Officers
Model decay timelines for Cesium-137 and Cobalt-60 to determine safe decommission windows, storage durations, and exposure thresholds.
