Example preset
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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.
How to use this calculator effectively
This guide helps you use Radioactive decay/dating calculator (half-life/ratio → age) in a repeatable way: define a baseline, change one variable at a time, and interpret outputs with explicit assumptions before you share or act on results.
How it works
The page applies deterministic logic to your inputs and shows rounded output for readability. Treat it as a comparison workflow: run one baseline case, adjust a single parameter, and measure both absolute and percentage deltas. If a result seems off, verify units, time basis, and sign conventions before drawing conclusions. This approach keeps your analysis reproducible across teammates and sessions.
When to use
Use this page when you need a fast estimate, a classroom check, or a practical what-if comparison. It works best for planning and prioritization steps where you need direction and magnitude quickly before investing in deeper modeling, manual spreadsheets, or formal external review.
Common mistakes to avoid
- Changing multiple parameters at once, which hides the true cause of output movement.
- Mixing units (percent vs decimal, monthly vs yearly, gross vs net) across scenarios.
- Comparing with another tool without aligning defaults, constants, and rounding rules.
- Using rounded display values as exact downstream inputs without re-checking precision.
Interpretation and worked example
Run a baseline scenario and keep that result visible. Next, modify one assumption to reflect your realistic alternative and compare direction plus size of change. If the direction matches your domain expectation and the size is plausible, your setup is usually coherent. If not, check hidden defaults, boundary conditions, and interpretation notes before deciding which scenario to adopt.
See also
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.
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