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.
Alcohol Consumption
Peak ETG estimated at 15,000 ng/mL (5,000 ng/mL per drink)
Time until the model is below each line
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 | Above 500 ng/mL |
| 1 | 3h | 7,500 ng/mL | Above 500 ng/mL |
| 2 | 6h | 3,750 ng/mL | Above 500 ng/mL |
| 3 | 9h | 1,875 ng/mL | Above 500 ng/mL |
| 4 | 12h | 938 ng/mL | Above 500 ng/mL |
| 5 | 15h | 469 ng/mL | 100–500 ng/mL |
ETG half-life in urine is about 3 hours
In urine, ETG drops by about half every 2–3 hours. This page uses 3 hours as a conservative model. The table is the default 3-drink run already in the calculator above (peak 15,000 ng/mL).
| Time After Last Drink | Half-Lives Elapsed | Est. ETG Level |
|---|---|---|
| Peak (just after drinking) | 0 | ~15,000 ng/mL |
| 3 hours later | 1 half-life | ~7,500 ng/mL |
| 6 hours later | 2 half-lives | ~3,750 ng/mL |
| 9 hours later | 3 half-lives | ~1,875 ng/mL |
| 12 hours later | 4 half-lives | ~938 ng/mL (still above 500) |
| About 14h 43m | ~4.9 half-lives | ~500 ng/mL |
| About 21h 41m | ~7.2 half-lives | ~100 ng/mL |
Peak is 5,000 ng/mL per standard drink. Half-life is 3 hours. Move the slider to match your drink count; the table above follows the same formula.
Why a 3-hour half-life can still mean a long window
Half-life is the time to cut the current level in half, not the time until a test cannot see ETG. A high peak needs many of those cuts before it sits under 500 or 100 ng/mL.
- From 15,000 ng/mL, this model needs about five half-lives (~15 hours) to sit under 500, and about seven (~22 hours) to sit under 100.
- Twice the drinks is a higher peak, not twice the hours. Going from 4 drinks to 8 adds about one extra half-life (~3 hours) in this formula, not a doubled wait.
- The 80-hour figure people quote is a maximum-case lab warning for heavy drinking and a sensitive cutoff. It is not what 3 drinks does in this table.
When this calculator does not apply
- Your half-life may be closer to 2 hours or 4 hours. Age, liver function, and genetics sit outside this slider.
- Peak is 5,000 ng/mL per standard drink because that is this site's model, not a number from your lab.
- How concentrated the urine is can move ng/mL without changing how fast the liver works. Extra water does not speed the half-life.
- The hours next to 500 and 100 are when this formula drops below that line. They are not a time to go get tested, and they are not a lab result.
Where the 3-hour number comes from
Published urinary ETG work often lands in a 2–3 hour half-life range. This site uses 3 hours on purpose, as a slower end of that range, with 5,000 ng/mL peak per standard drink and the common 100 / 500 ng/mL lines.
Wurst FM et al. (2006) Ethyl glucuronide — update. Forensic Science International. Same model as the formula page.
If you need something this page does not do
Frequently Asked Questions
Each row is one half-life in this model. The pattern is always 100% → 50% → 25% → 12.5%. Three-hour steps make that easy to see, and they line up with when the estimate crosses 500 ng/mL and 100 ng/mL.
No. The formula halves whatever you start with, every 3 hours. Doubling drinks doubles the peak, which adds about one extra half-life (~3 hours) before the same cutoff, not a doubled clock. Change the slider from 4 to 8 if you want to see that in the table.
This calculator shows ETG decay with the half-life formula for education only. Individual metabolism varies. This is not medical or legal advice. For case-specific testing questions, consult a healthcare provider, legal professional, lab, or testing program.