EDUCATIONAL TOOL — NOT MEDICAL ADVICE Based on published Society of Hair Testing (SoHT) consensus cutoffs — not a substitute for a lab result.
Free Tool

Hair Follicle Alcohol Test Calculator

Check detection windows for hair testing — hair follicle alcohol tests reflect a lookback window based on hair length, not a same-day decay curve.

Fact-checked by the CalcGrain Editorial Team · Sources: NIAAA, SAMHSA, Methodology
💡 Unlike urine ETG, hair follicle testing can't reliably estimate a number from "how many drinks" — it reflects a chronic pattern over the growth window, not a single session. This tool calculates your lookback window and explains what published cutoff tiers generally mean.
✂️ Labs typically request hair cut close to the scalp. The standard single-segment test uses about 1.5 inches (~3.9 cm), covering roughly the most recent 90 days. Longer hair can sometimes be tested in separate segments for a month-by-month history.
💇 Enter hair length to see the lookback window.
Estimated Lookback Window
— days
Effective ETG Sensitivity
100%
Earliest Date This Could Reveal
—
Published SoHT Cutoff Tiers (Reference)

How Hair Follicle Alcohol Testing Works

This calculator estimates a lookback window from hair length. It does not interpret a laboratory EtG or FAEE concentration, and it does not convert drink counts into a hair result. Head-hair growth on this tool follows the same rates used in the calculator (~1.25 cm / ~0.49 in per month). Labs often take a proximal scalp segment of about 1.5 inches (~3.9 cm) as a roughly 90-day panel; SoHT’s 3 cm baseline is about three months. Longer hair may be split into segments. Details: hair follicle alcohol test guide.

Understanding EtG Hair Cutoff Levels

The on-page legend uses this tool’s published reference tiers: 7 pg/mg (any detectable consumption) and 30 pg/mg (SoHT consensus cutoff — chronic/excessive use). Guides on this site also cite SoHT hair-EtG lines of ≤5 pg/mg (does not contradict claimed abstinence) and ≥30 pg/mg (strongly suggesting chronic excessive drinking as SoHT defines it). Those are hair pg/mg figures, not urine ng/mL. This page does not turn a lab number into a pass/fail.

Frequently Asked Questions

Can body hair be used?

Some labs accept body hair with different growth rates — confirm with the testing facility.

Does hair color matter?

Bleaching, dyeing, and perming can reduce hair ETG levels significantly. Melanin and cosmetic treatments can affect some assays; labs account for this differently.

Will one night of drinking show in hair?

Chronic markers reflect patterns over weeks to months. A single episode is unlikely to mimic heavy chronic exposure on a hair panel.

How far back does a 3 cm hair alcohol test go?

At about 1 cm per month, 3 cm is often discussed as roughly 90 days. Confirm the lab’s growth assumption.

Will bleaching my hair beat a hair ETG test?

Cosmetic treatments can lower measured hair ETG, which is why labs document treatments. Do not treat bleaching as a strategy to hide use.

Is hair testing for one night of drinking?

Hair markers are built for patterns over weeks to months, not a single calendar night.

Can I use beard or body hair?

Some labs accept alternative sites with different growth rates. Ask the collection site before assuming scalp rules apply.

What is segmental hair testing?

The sample is cut into lengths from root to tip to approximate month-by-month exposure when the hair is long enough.

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