EtG Hair Follicle Calculator
Estimate your EtG classification zone and detection window — grounded in SoHT consensus guidelines and peer-reviewed research.
Hair follicle EtG (Ethyl Glucuronide) testing detects chronic alcohol consumption patterns, not single episodes. EtG is a direct alcohol metabolite that gets permanently incorporated into the hair shaft as it grows (~1 cm/month). The internationally accepted standard (Society of Hair Testing / SoHT) uses a 3 cm proximal segment (~90 days of history) and classifies results into three evidence-based zones:
| EtG Level in Hair | SoHT Interpretation | Ethanol Context |
|---|---|---|
| < 5 pg/mg | Abstinence or very occasional/incidental use | ~0–16 g ethanol/day (varies widely) |
| 5 – 30 pg/mg | Regular moderate/social consumption | ~16–60 g ethanol/day (varies widely) |
| ≥ 30 pg/mg | Chronic excessive consumption | ≥ 60 g ethanol/day over months (SoHT threshold) |
Sources: SoHT Consensus 2022; Crunelle et al., 2019 (NIH); Pragst & Balikova, Drug Alcohol Depend.
• Bar = estimated median | Shaded band = plausible population range given individual variability | Green line = 5 pg/mg Red line = 30 pg/mg (chronic threshold)
SoHT Classification Zones
| EtG (pg/mg) | SoHT Category | Ethanol Context | Your Result |
|---|
Research reference: Occasional drinkers (1–2 days/wk) → median ~6.3 pg/mg; Repeated drinkers (3–5 days/wk) → median ~11.3 pg/mg (NIH-indexed university study). 100 g EtOH/week group: variable, many below 30 pg/mg.
- Step 1 – Ethanol intake (g/day): Your daily ethanol intake is converted to a weekly total in grams.
- Step 2 – SoHT zone mapping: The WHO/SoHT threshold of ≥ 60 g/day = chronic (≥30 pg/mg) is used as the reference anchor.
- Step 3 – Range estimation: A population-level range is derived from controlled study medians (abstainers: ~0.5 pg/mg; occasional: ~6.3 pg/mg; repeated: ~11.3 pg/mg; heavy/chronic: 30–150+ pg/mg). High individual variability is modeled as ±40–60% of median.
- Step 4 – Modifiers applied: Sex (+15% for female per incorporation research); hair treatment (−30% mild, −50% heavy bleaching); binge pattern (+10% per episode/month based on peak BAC effect); duration factor (pattern must be sustained “several months” for chronic threshold to apply per SoHT).
- Step 5 – Detection window: Hair segment (cm) ÷ growth rate (1.0 cm/month standard) = months of history. The standard 3 cm / 1.0 cm per month = 90 days.
- Important: Since no peer-reviewed formula translates exact grams to precise pg/mg values, this tool outputs a research-informed range, not a single number. The SoHT interprets results categorically, not numerically.
The Science Behind Hair Follicle EtG Testing
The Society of Hair Testing (SoHT) — the international body governing hair biomarker testing — established three evidence-based EtG concentration zones:
- < 5 pg/mg: Consistent with abstinence or very infrequent/incidental alcohol exposure. Note: abstainers in controlled studies showed a median of ~0.5 pg/mg.
- 5 – 30 pg/mg: Consistent with regular social/moderate alcohol consumption. Research finds occasional drinkers (1–2 days/week) cluster around 6–7 pg/mg; repeated drinkers (3–5 days/week) around 11–15 pg/mg.
- ≥ 30 pg/mg: Consistent with chronic excessive alcohol consumption, defined by the WHO/SoHT as an average of ≥ 60 g of pure ethanol per day over several months.
The SoHT explicitly states: “It is not possible to accurately translate a specific pg/mg value into an exact number of drinks per day.” Results represent patterns of consumption, not quantities.
Source: SoHT Consensus on EtG in Hair (2022); Crunelle et al., Drug Alcohol Depend (2019); Pragst & Balikova, Forensic Sci Int (2006).
Scalp hair grows at a research-validated average rate of ~1 cm per month (0.5 inches/month). This is the standard used by all accredited forensic laboratories.
- Standard test: 3 cm proximal (scalp-closest) segment = ~3 months (90 days) of history.
- Segmented analysis: Labs can analyze 1 cm segments independently, giving a month-by-month profile.
- Slow growth (0.8 cm/mo): 3 cm = ~3.75 months of history (window extends).
- Fast growth (1.2 cm/mo): 3 cm = ~2.5 months of history (window contracts).
- Body hair: Grows much slower — can reflect use up to 12 months back, but is rarely used in standard testing.
Key limitation: A positive result in the proximal 3 cm cannot pinpoint when exactly in the 90-day window drinking occurred — only that it occurred.
Source: Kintz P., Forensic Sci Int (2012); SoHT Collection Guidelines; NIH Hair Testing Overview.
The only reliable data comes from controlled dosing studies and population surveys. Key findings:
- Abstainers: Median EtG ~0.5 pg/mg (range <0.21–4.5 pg/mg) — confirming the <5 pg/mg abstinence zone.
- Occasional drinkers (1–2 days/week): Median ~6.3 pg/mg in a university student study (NIH-indexed).
- Repeated drinkers (3–5 days/week): Median ~11.3 pg/mg in the same study.
- 100 g ethanol/week group (controlled, 12 weeks): Variable results; many remained below 30 pg/mg — demonstrating why individual variability makes prediction unreliable.
- 16–32 g/day for 3 months: Most subjects remained below the 30 pg/mg chronic threshold; some didn’t even reach the 5 pg/mg abstinence zone.
- Chronic excessive (>60 g/day): Strongly associated with ≥30 pg/mg, but some chronic drinkers remain below due to rapid hair growth or cosmetic treatments.
Conclusion: There is no linear formula. The same weekly intake can produce EtG values that span more than one SoHT zone across different individuals.
Source: NIH-indexed dosing study (PMC); University student survey (NIH); Høiseth et al., Alcohol Clin Exp Res.
- Bleaching / lightening: Can reduce EtG by 40–60% or more, potentially pushing results below the 30 pg/mg or even 5 pg/mg thresholds.
- Chemical relaxers / perms: Reduce EtG by ~30–50% through disruption of the keratin matrix.
- Dyeing/coloring: Mild reduction (~15–25%). Most labs account for this during interpretation.
- Frequent washing (daily): Some studies suggest frequent shampooing may reduce EtG slightly, though effect is contested.
- Fast hair growth: Dilutes EtG across a longer shaft; the same ethanol intake produces a lower concentration per cm.
- Dark hair color: Interestingly, dark (melanin-rich) hair binds EtG more readily than blonde/light hair — meaning lighter hair may show lower results for the same intake.
Source: Pragst & Balikova (2006); Kintz et al., Ann Toxicol Anal; SoHT interference guidance.
Yes — the pattern of drinking matters, not just the total volume:
- High-volume binge episodes (5+ drinks at once) produce higher peak blood alcohol concentrations (BAC), which temporarily flood the bloodstream with EtG, leading to higher incorporation into the hair shaft during that growth period.
- The same weekly total spread across daily moderate drinking may produce lower EtG levels in hair than concentrated into 1–2 binge episodes.
- Binge drinking is therefore associated with higher-than-expected EtG levels relative to average weekly intake.
- The SoHT notes that drinking pattern (daily sipping vs. periodic heavy use) is a recognized source of variability in hair EtG interpretation.
Source: Wurst et al., Alcohol Alcohol; SoHT consensus statement on pattern vs. volume.
How the EtG Hair Follicle Calculator Works
This calculator gives an estimated EtG (ethyl glucuronide) level in pg/mg based on how much and how often you drank over the past few months. EtG is a metabolite of alcohol that gets incorporated into growing hair, so a hair sample can reflect alcohol use over a longer window than urine or blood tests.
Enter your typical drinking pattern month by month, and the tool shows a rough range you can compare against standard cutoff levels.
EtG Hair Test Cutoff Levels
| Result (pg/mg) | Typical Interpretation |
|---|---|
| Below 5 | Consistent with abstinence or very light drinking |
| 5 – 30 | Possible light to moderate drinking |
| Above 30 | Suggests repeated or excessive drinking |
These cutoffs follow the Society of Hair Testing (SoHT) consensus guidelines. Individual labs may use slightly different thresholds.
How Far Back Does a Hair Test Look?
Head hair grows about 1 cm per month. A standard 3 cm sample therefore covers roughly 3 months of alcohol use. A longer segment can cover a longer period.
What Can Affect Your Result?
- Hair growth rate and hair length
- Bleaching, dyeing, or heavy chemical treatments
- Hair products containing ethanol
- Individual differences in metabolism
Important Disclaimer
This calculator provides an educational estimate only. It is not a laboratory result, a medical diagnosis, or a substitute for professional advice. Actual EtG levels vary from person to person. For official testing or health decisions, consult a certified laboratory or healthcare professional.
FAQ
How accurate is this EtG hair calculator?
It gives a general estimate based on drinking patterns. Real lab results can differ because of individual biology and hair characteristics.
What does 30 pg/mg mean on an EtG hair test?
It is the commonly used cutoff that suggests chronic excessive alcohol consumption.
Can hair dye change EtG results?
Yes. Bleaching and chemical treatments can reduce EtG levels in hair.
How long does alcohol stay detectable in hair?
Roughly 1 month per centimeter of hair, so a 3 cm sample usually reflects about 3 months.