Example preset
Choose a preset to fill the form and refresh results instantly.
Inputs
Results
| Half-life number n (t/T) | — |
|---|---|
| Remaining amount N | — |
| Survival rate r (N/N0) | — |
|---|---|
| Survival rate (%) | — |
Era conversion (optional)
| Estimated age (counted backwards from base year) | — |
|---|---|
| Estimated BP (1950 standard) | — |
*Year/BP is an uncalibrated approximate display (for learning purposes).
Details (decay constant λ / average life τ)
| Decay constant λ | — |
|---|---|
| Average lifespan τ | — |
| year definition | — |
Graph (time → survival rate)
The graph shows the decay of survival rate over time. The linear display shows the survival rate %, and the logarithmic display shows the survival rate r.
When input, the survival rate curve against time will be displayed.
| time | Survival rate r | Survival rate (%) |
|---|---|---|
| Displays representative points after displaying the graph. | ||
Calculation procedure
入力すると計算手順を表示します。
Assumptions & limits
- This is an approximation based on an idealized exponential decay model (single decay).
- In the practice of radiometric dating, additional analyzes such as establishment of a closed system, initial conditions, isotopic ratios, and corrections are required.
- The year (yr) is fixed as the Julian year (365.25 days).
- The input values are calculated within the browser and can be reproduced in the shared URL.
Study notes (half-life and dating)
This tool uses simple exponential decay N(t)=N0·exp(-λt)（λ=ln2/T) is an approximation using Suitable for checking formulas and understanding orders.
Examples of main nuclides and uses
| nuclide | half-life | Main usage examples |
|---|---|---|
| Carbon-14 (C-14) | 5,730 years | Archeology and paleoenvironmental samples (tens of thousands of years scale) |
| Potassium-40 (K-40) | 1.248 billion years | Geological age estimation of volcanic rocks, etc. |
| Uranium-238 (U-238) | 4.468 billion years | Earth history scale chronological discussion |
| Iodine 131 (I-131) | 8 days | Confirmation of decay of short-lived nuclides |
Differences from practice (important)
- Radiometric dating verifies the establishment of a closed system, initial conditions, contamination, equipment correction, etc.
- The C-14 era requires a calibration curve, which may not match the simple equation.
- The Western calendar/BP conversion in this calculator is an approximate learning display and cannot be used as a reported value.
FAQ
Is this age the same as the actual radiometric dating?
No. This calculator uses an ideal exponential-decay model. Real radiometric dating also needs checks for closed-system behavior, initial conditions, isotope ratios, and corrections.
What is the definition of "year"?
This tool calculates Julian year (365.25 days) as one year.
What are the units of initial amount N0 and remaining amount N?
Please enter in the same unit (g, mol, number, etc.). The ratio r=N/N0 is dimensionless.
How is the BP (Before Present) display calculated?
It shows uncalibrated BP by converting the estimated event year to a 1950 baseline. Research use requires calibration curves and measurement checks.
What should I do first on this page?
Start with the minimum required inputs or the first action shown near the primary button. Keep optional settings at defaults for a baseline run, then change one setting at a time so you can explain what caused each output change.
How to use Radioactive decay/dating calculator (half-life/ratio → age) effectively
What this calculator does
This page is for estimating outcomes by changing inputs in one controlled workflow. The model keeps your focus on variables, not output shape. Start with stable assumptions, then test sensitivity by changing one key input at a time to observe directional impact.
Input meaning and unit policy
Each input has an expected unit and a typical range. For reliable interpretation, check whether you are using the same unit system, period, and base assumptions across all runs. Unit mismatch is the most common source of unexpected drift in numeric results.
Use-case sequence
A practical sequence is: first run with defaults, then create a baseline log, then run one alternative scenario, and finally compare only the changed output metric. This sequence reduces cognitive load and prevents false pattern recognition in early experiments.
Common mistakes to avoid
Avoid changing too many variables at once, mixing incompatible data sources, and interpreting a one-time output without checking robustness. A single contradictory input can flip conclusions, so keep each experiment minimal and document assumptions as part of your note.
Interpretation guidance
Review both magnitude and direction. Direction tells you whether a strategy moves outcomes in the desired direction, while magnitude helps you judge practicality. If both agree, you can proceed; if not, rebuild the baseline and verify constraints before deciding.
Related tools
- AQI (Air Quality Index) Calculator (US EPA) | CalcBEcalculators, aqi-calculator, calculator, en
- Calculate epicenter distance and occurrence time from P | CalcBEcalculators, ps-wave-distance, calculator, en
- Distance/azimuth calculator for two latitude | CalcBEcalculators, latlong-distance-bearing, calculator, en
- DO Saturation and BOD/COD Calculator | CalcBEcalculators, water-quality-do-bod-cod, calculator, en
- Earthquake b-value calculator (Gutenberg-Richter) | CalcBEcalculators, earthquake-b-value, calculator, en
Comments
Comments are only loaded on request (Giscus).