ETG Half-Life Calculator
How long is ETG half life? See how ETG drops every 3 hours — this calculator shows the cutoff math, half-life by half-life.
Quick Answer: How Long is ETG Half-Life?
ETG has a half-life of approximately 3 hours in urine. Every 3 hours, ETG levels drop by 50%. Here's how a 4-drink session (~20,000 ng/mL peak) decays over time:
| Time After Last Drink | Half-Lives Elapsed | Est. ETG Level |
|---|---|---|
| Peak (right after drinking) | 0 | ~20,000 ng/mL |
| 3 hours later | 1 half-life | ~10,000 ng/mL |
| 6 hours later | 2 half-lives | ~5,000 ng/mL |
| 12 hours later | 4 half-lives | ~1,250 ng/mL |
| 16 hours later | ~5.3 half-lives | ~500 ng/mL (near a standard cutoff) |
| 23 hours later | ~7.6 half-lives | ~100 ng/mL (near a stricter cutoff) |
Numbers use the project's calculator model (5,000 ng/mL peak per drink, 3-hour half-life). Individual half-life varies 2-3 hours depending on metabolism, hydration, and body composition. Use the full calculator below for your exact drink count.
Alcohol Consumption
Peak ETG estimated at 15,000 ng/mL (5,000 ng/mL per drink)
Estimated Cutoff Timing
Half-Life Formula
- Peak:Initial level (15,000 ng/mL)
- t:Hours since last drink
- Half-life period:3h
Decay Schedule
| Half-Lives | Time Elapsed | Est. ETG | Status |
|---|---|---|---|
| 0 | 0h | 15,000 ng/mL | Likely Detected |
| 1 | 3h | 7,500 ng/mL | Likely Detected |
| 2 | 6h | 3,750 ng/mL | Likely Detected |
| 3 | 9h | 1,875 ng/mL | Likely Detected |
| 4 | 12h | 938 ng/mL | Likely Detected |
| 5 | 15h | 469 ng/mL | Uncertain |
What is ETG Half-Life?
Half-life means "the time it takes to cut in half." For ETG, that's roughly 2-3 hours. Every 3 hours, whatever ETG is in your system drops by 50%.
Here's what that looks like:
This pattern continues as ETG levels decline. The more you start with, the longer it takes to fall below common cutoffs.
How the Decay Actually Works
Let's walk through a real scenario so you can see this formula in action.
Real Example: Friday Night Drinks
Notice how it takes about 18 hours just to drop below 500 ng/mL from 4 drinks in this model. Heavier drinking means a longer estimated detection window.
This Calculator vs. The Main ETG Calculator
We have two ETG tools. Here's which one to use:
Main ETG Calculator
Quick answer: "How does my estimate compare with common cutoffs?"
When you need a fast cutoff comparison
Half-Life Calculator
Full picture: "How does ETG decay?"
When you want to understand the timeline
Most people start with the main calculator. Come here when you want to see exactly how your ETG level changes hour by hour.
The Science Behind These Numbers
The 2-3 hour half-life comes from peer-reviewed research in forensic toxicology. A 2015 study in the Journal of Analytical Toxicology found urinary ETG half-life averaged 2.5 hours across participants. We use 3 hours as a conservative estimate, but your real ETG decline can differ.
Reference: Helander et al., Journal of Analytical Toxicology, 2015
Practical Tips for Using This Calculator
Understanding half-life is useful, but here's how to apply it in real situations:
Treat Estimates Carefully
Calculator estimates are averages. Real results can differ because of metabolism, liver function, sample concentration, and lab rules.
Don't Rely on One Number
Your personal half-life could be 2 hours or 4 hours. Without lab testing, you won't know your exact rate. Plan for the slower end of the range.
Hydration Matters (A Little)
Staying hydrated doesn't speed up metabolism, but it can affect urine concentration. Don't over-hydrate right before a test — it may flag as dilute.
Heavy Drinking = Longer Wait
Each additional drink adds to your peak level. Going from 4 drinks to 8 drinks doesn't just double your wait time — it can add 12+ hours because you're starting from a much higher peak.
Remember: This tool shows the math behind ETG decay. It cannot account for your individual metabolism, liver function, or other personal factors.
How to Use
- 1
Set the number of standard drinks using the slider (1 beer = 1 wine glass = 1 shot).
- 2
View the peak ETG level calculated from your drink count.
- 3
Check the decay table to see how ETG drops at each half-life interval.
- 4
Note the estimated time to reach both 500ng and 100ng cutoffs.
- 5
Remember: actual results vary by individual. Consult the relevant testing program, lab, healthcare provider, or legal professional for case-specific guidance.
Frequently Asked Questions
Half-life is the time required for ETG concentration to decrease by 50%. Research shows ETG has a half-life of approximately 2-3 hours. We use 3 hours as a conservative estimate. After each half-life period, only half the previous amount remains in your system.
It depends on your starting level and the test's cutoff. Generally, after 7-10 half-lives (21-30 hours), many substances are much lower than their starting concentration. For heavy drinking with high peak ETG, the model may need 8+ half-lives to reach below 100ng/mL. Light drinking can fall below cutoffs faster.
Each row represents one complete half-life cycle. The pattern is always the same: 100% → 50% → 25% → 12.5% → 6.25%. Using half-life intervals makes the math simple and lets you see when the model reaches common cutoff levels.
No — it's an average. Your actual half-life depends on liver function, age, genetics, hydration, and overall health. Some people metabolize ETG faster (shorter half-life), others slower. We use 3 hours as a conservative estimate, but it is still only a model.
Use the main calculator when you want a quick cutoff comparison. Use this half-life calculator when you want to understand the science — why ETG levels decline the way they do, and how the math works behind the scenes.
Related Tools
ETG Urine Test Calculator
Quick cutoff estimate tool
ETG Detection Time Chart
Visual breakdown by drinks
Realistic ETG Detection Times
Why 80-hour claims are maximum-case, not typical
ETG Calculation Formula
The science behind the math
ETG Cutoff Levels
How 100, 200, 300, and 500 ng/mL change results
Standard Drink Guide
Know exactly what counts as one drink
This calculator demonstrates ETG decay using the half-life formula for educational purposes only. Individual metabolism varies significantly — actual results may differ by 20-30% or more. This is not medical or legal advice. For case-specific testing questions, consult a healthcare provider, legal professional, lab, or testing program.