Key calculations

Baseline Detection Window

The initial detection window is estimated from the number of standard drinks processed through a simplified pharmacokinetic model. Each standard drink adds roughly 12–24 hours to the potential detection window depending on the drinking pattern.

Pattern Adjustment

The drinking pattern modulates the baseline estimate. Single-session drinks are concentrated in a short window, extending the peak EtG level. Extended-window drinks spread metabolism over time, shortening the tail. Heavy-binge sessions produce a higher peak and longer overall detection curve.

Cutoff Scaling

Higher cutoffs (500 ng/mL) produce shorter detection windows because only higher metabolite concentrations register as positive. Lower cutoffs (100 ng/mL) are more sensitive and produce longer windows. The calculator adjusts estimates proportionally using established reference ratios.

Elapsed Time Decay

Hours since last drink are subtracted from the raw estimate to produce a remaining window. If elapsed time exceeds the estimated window, the result shows the subject is already past the likely detection range.

Reference ranges

Single Session (1–3 drinks)

Typical detection window of 24–48 hours at 500 ng/mL cutoff, extending to 48–72 hours at 100 ng/mL. Light to moderate drinking in a short period produces the shortest overall detection times.

Extended Window (3–6 drinks)

Typical detection window of 36–60 hours at 500 ng/mL cutoff, extending to 60–80 hours at 100 ng/mL. Drinking spread over many hours produces a flatter but longer elimination curve.

Heavy Binge (6+ drinks)

Typical detection window of 48–72 hours at 500 ng/mL cutoff, extending to 72–96 hours at 100 ng/mL. High-volume sessions produce the highest peak metabolite levels and the longest detection windows.

Cutoff Sensitivity

The 500 ng/mL cutoff is the least sensitive and produces the shortest windows. 250 ng/mL is a common intermediate threshold. 100 ng/mL is the most sensitive and produces the longest windows. Laboratory policies on reporting positive vs. negative vary and affect real-world results.

How to use it

1. 1.Select your drinking patternChoose Single Session for drinks consumed within 1–2 hours, Extended Window for drinks spread across many hours, or High-Intensity for sustained high-volume sessions. The pattern adjusts the peak EtG concentration and elimination curve.
2. 2.Enter the number of drinksEnter the total number of standard drinks consumed (12 oz beer, 5 oz wine, or 1.5 oz spirits = 1 standard drink). Be as accurate as possible — this is a primary driver of the detection window.
3. 3.Enter time since last drinkInput the number of hours that have passed since you finished your last drink. This is subtracted from the raw estimate to determine the remaining detection window.
4. 4.Choose your test cutoffSelect 100, 250, or 500 ng/mL to match your test, or choose Custom to enter a specific cutoff between 50 and 1000 ng/mL. Lower cutoffs produce longer detection windows.
5. 5.Review the detection windowRead the likely-negative hours (when you will probably test below cutoff) and the conservative estimate (a more cautious upper bound). The preset comparison cards show how different cutoffs change the window.
6. 6.Check the risk bandThe risk band (Low, Borderline, or High) gives a quick summary of where you fall relative to the chosen cutoff. Use the summary text for context about your specific inputs.