ETG Half-Life Calculator
See exactly how ETG drops over time. This tool shows the math behind your clearance — hour by hour, half-life by half-life.
Alcohol Consumption
Peak ETG estimated at 15,000 ng/mL (5,000 ng/mL per drink)
Estimated Clearance Time
Half-Life Formula
- Peak:Initial level (15,000 ng/mL)
- t:Hours since last drink
- Half-life period:3h
Decay Schedule
| Half-Lives | Time Passed | 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 until ETG becomes undetectable. The more you start with, the longer it takes to clear.
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. Heavier drinking = much longer wait.
This Calculator vs. The Main ETG Calculator
We have two ETG tools. Here's which one to use:
Main ETG Calculator
Quick answer: "Will I pass?"
When you need a fast risk check
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 — your actual clearance might be faster.
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:
Add Buffer Time
Calculator estimates are averages. For important tests, add 20-30% extra time beyond what the calculator shows. If it says 24 hours, wait 30 hours to be safe.
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 clearance varies by individual. Add buffer time for important tests.
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), most substances become undetectable. For heavy drinking with high peak ETG, you may need 8+ half-lives to reach below 100ng/mL. Light drinking clears faster — sometimes in just 4-5 half-lives.
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 quickly see how long until you hit your target level.
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, so your actual clearance might be faster.
Use the main calculator when you just need to know if you'll pass. Use this half-life calculator when you want to understand the science — why clearance takes as long as it does, and how the math works behind the scenes.
Related Tools
This calculator demonstrates ETG decay using the half-life formula for educational purposes only. Individual metabolism varies significantly — actual clearance times may differ by 20-30%. This is not medical or legal advice. For important decisions, consult a healthcare provider and add extra buffer time beyond estimates shown.