EtG 100 ng/mL Calculator — Estimate Urine EtG Detection

If your urine alcohol test uses a 100 ng/mL EtG cutoff, this calculator provides a research-informed educational estimate based on the drinking information you enter. It is designed to help explain how alcohol exposure, body characteristics, and elapsed time can relate to urine ethyl glucuronide (EtG) testing.

The result is an estimate, not a prediction of your laboratory result. Actual urine EtG concentrations can vary substantially between people and between samples because of factors such as drinking pattern, time since alcohol consumption, urine concentration, individual metabolism, and the testing method used by the laboratory.

EtG, or ethyl glucuronide, is a metabolite formed after the body processes ethanol. Unlike blood or breath alcohol testing, which primarily reflects alcohol currently present in the body, urine EtG testing is used to identify recent alcohol exposure after ethanol itself has largely been eliminated.

A 100 ng/mL cutoff is relatively sensitive. Research comparing EtG cutoff concentrations has found that lower cutoffs generally increase sensitivity for detecting recent drinking while reducing specificity compared with higher cutoffs.

What Is an EtG 100 ng/mL Test?

EtG stands for ethyl glucuronide, a minor metabolite your liver produces when it breaks down ethanol — the alcohol in beer, wine, and spirits. Only a small fraction of the alcohol you drink gets converted into EtG, but that fraction is useful precisely because it lingers in urine long after the alcohol itself, and any intoxicating effect, has cleared. That's the whole reason urine EtG testing exists as a distinct category from breath or blood alcohol testing: it answers "did this person drink recently," not "is this person impaired right now."

EtG concentration is reported in nanograms per milliliter (ng/mL) — a measure of how much EtG is present relative to the volume of urine in the sample. A cutoff is simply the number a lab or program has decided to treat as the line between a negative and positive result. Anything reported below the cutoff is called negative; anything at or above it is called positive, even though EtG concentration itself is a continuous value, not a yes/no switch.

Different programs land on different cutoffs for different reasons. A workplace program mainly worried about heavy, recent drinking might use a higher threshold like 500 ng/mL to avoid disputes over incidental exposure. A family court or probation program enforcing strict abstinence often prefers a lower threshold — commonly 100 ng/mL — because it's more likely to catch lighter drinking or drinking that happened a bit further in the past.

It's worth being precise about what a cutoff is not. A cutoff is not the same thing as an exact detection time. "100 ng/mL" tells you where the line is drawn on a concentration scale; it doesn't by itself tell you how many hours after drinking a specific person's sample will cross that line, because concentration and elapsed time interact differently for every individual.

How the EtG 100 ng/mL Calculator Works

The calculator draws on research-informed, population-level relationships between alcohol exposure and typical EtG behavior over time — not a proprietary formula that claims to reverse-engineer your exact biology. In practice, it considers factors such as:

• Alcohol consumed (standard drinks)
• Beverage alcohol concentration
• Body weight
• Sex
• Age
• Time since your last drink
• Drinking duration
• Previous alcohol exposure, where relevant
• The urine concentration reference you select

Feeding these into the tool produces an estimate of how your scenario compares to the 100 ng/mL reference point — categorized in broad terms rather than as a precise number. The calculator cannot tell you an exact urine EtG concentration, because that number depends on real-time physiological variables (hydration at collection, individual metabolic rate, kidney function) that no input form can capture. What it offers instead is a way to see how the general research on alcohol exposure and detection time applies to a scenario like yours.

If you want a broader starting point before narrowing in on the 100 ng/mL threshold specifically, the general-purpose EtG calculator is a good first stop, and the Advanced ETG Calculator lets you test your numbers against multiple cutoff levels side by side.

Understanding the 100 ng/mL EtG Cutoff

In lab-testing terms, 100 ng/mL is considered a comparatively sensitive cutoff. Sensitivity and specificity are two different properties of any test, and it helps to keep them separate:

• Sensitivity describes how good a test is at catching true positives — in this case, actual recent drinking, including light drinking. A lower cutoff like 100 ng/mL is more sensitive: it's positioned to flag smaller amounts of EtG, which means it can pick up lighter drinking, or drinking that happened somewhat further back, that a higher cutoff would miss.
• Specificity describes how good a test is at correctly returning a negative when someone genuinely didn't drink. Lower cutoffs tend to trade away some specificity, because they're more likely to register incidental, non-beverage sources of trace ethanol — think alcohol-based hand sanitizer, mouthwash, or certain fermented foods — as a low-level positive.

That trade-off is exactly why a 100 ng/mL result shouldn't be read, on its own, as proof of beverage alcohol consumption without considering the broader context: recent product use, medications, diet, and how the sample was collected all matter. It's also why laboratory methodology counts for a lot. An initial immunoassay screen and a confirmatory method like LC-MS/MS (liquid chromatography-tandem mass spectrometry) don't carry identical reliability, and a result near a sensitive cutoff is exactly the situation where confirmatory testing is most useful.

None of this means 100 ng/mL is an unreliable or arbitrary number — sensitive cutoffs are chosen deliberately, usually in settings where the goal is genuine, strict abstinence monitoring. It just means the number needs to be read with its trade-offs in mind, not treated as an infallible verdict.

How Long Can EtG Be Detected at 100 ng/mL?

There's no single number of hours that applies to everyone at this cutoff, and any source promising one guaranteed figure is oversimplifying. What published research does support is a range, shaped by several variables working together:

• Amount of alcohol consumed — higher intake produces a higher EtG peak, which generally takes longer to fall back below a sensitive cutoff.
• Timing — when drinking occurred relative to collection, and whether drinks were spread out or consumed quickly.
• Repeated or ongoing drinking — drinking across a longer stretch, rather than a single sitting, can push the window later.
• Individual variation — liver enzyme activity, kidney function, and general metabolism differ from person to person.
• Urine concentration — a more dilute sample generally reads lower, independent of how much was actually metabolized.
• Laboratory cutoff and assay — the specific method and threshold a lab uses shapes where the line falls.
• Specimen characteristics — collection timing and handling can influence the reported number.

Given all of that, the most defensible way to summarize the research is this: studies on EtG kinetics show substantial variation depending on dose and elapsed time, and detection at sensitive cutoffs like 100 ng/mL commonly extends into the range of roughly one to several days after drinking, with lighter drinking generally clearing sooner and heavier drinking extending closer to the upper end of published detection windows. That's a range, not a guarantee — and it's exactly what the calculator is built to help you reason through for your own inputs, rather than relying on a single rule of thumb.

For more background on how detection windows are studied and reported, how EtG testing works walks through the testing process in detail.

EtG 100 ng/mL vs 200 ng/mL vs 500 ng/mL

Lower cutoffs generally detect lower EtG concentrations, which means they can catch lighter or older drinking — but that added sensitivity comes with more interpretive uncertainty, since a low-level reading near a sensitive cutoff is harder to attribute with confidence to beverage alcohol alone. No cutoff in this table is universally "better." Each one reflects a different balance between catching true drinking and minimizing disputed or incidental positives, and the right one depends entirely on what a given program is trying to monitor.

Factors That Affect Urine EtG Results

A measured EtG concentration is the product of several variables layered on top of each other:

• Alcohol dose — more consumed generally means a higher peak and a longer window above any given cutoff.
• Time since drinking — EtG concentration falls over time as it's cleared, but not at a perfectly linear or identical rate for everyone.
• Drinking pattern — a single sitting versus drinking spread across several hours can produce different concentration curves.
• Urine dilution — this deserves particular attention. Because EtG is reported as a concentration (nanograms per milliliter), the amount of fluid in the sample directly affects the number, independent of how much EtG your body has actually produced. Drinking large amounts of water before a test can lower the measured ng/mL value in that single sample without changing the total EtG your body is processing — and labs commonly check creatinine or specific gravity precisely to flag samples that look artificially diluted.
• Individual metabolism — enzyme activity varies from person to person and affects how quickly ethanol is converted to EtG and cleared.
• Kidney handling — since EtG is excreted through urine, kidney function influences clearance.
• Assay characteristics — different testing methods have different sensitivity and precision.
• Specimen handling — collection and storage conditions can matter for result integrity.
• Non-beverage ethanol exposure — trace ethanol from certain personal-care products or foods can occasionally register at sensitive cutoffs.

Urine dilution in particular is a point of frequent confusion, so it's worth restating plainly: diluting a sample doesn't reduce the alcohol your body has processed — it only changes the concentration reading of that one sample, and a flagged dilute result can carry its own consequences depending on the program's rules.

Why Two People Can Have Different EtG Results

Imagine two people who each had the same number of drinks over a similar timeframe. One is tested 24 hours later, the other 36 hours later. Even with identical alcohol intake, their EtG readings could differ substantially — one might sit comfortably below a 100 ng/mL cutoff, while the other is still near or above it.

Body size plays a role, since a larger body volume generally dilutes peak alcohol exposure somewhat differently than a smaller one. So does the concentration of the urine sample itself: one person arriving well-hydrated may produce a more dilute sample than someone who hasn't had much fluid recently, independent of how much alcohol either of them actually drank. Add in ordinary biological variation in liver enzyme activity and kidney clearance, and it's easy to see how two broadly similar drinking histories can land on two different sides of a sensitive cutoff. None of this reflects imprecision in the test itself — it reflects the reality that concentration-based testing is inherently sensitive to individual, moment-to-moment physiology, which is exactly why population averages can't be treated as personal predictions.

How to Use the EtG 100 ng/mL Calculator

1. Enter the drinks consumed — the number of standard drinks involved.
2. Enter alcohol percentage and volume when necessary — for anything outside a standard drink.
3. Enter body weight.
4. Enter age and sex — both factor into the population-level relationships the calculator draws on.
5. Enter time since your last drink.
6. Add previous drinking information when relevant — useful if drinking occurred across more than one session.
7. Select the approximate urine concentration if known.
8. Run the calculation.
9. Interpret the result as an estimate, not a laboratory prediction — the categories describe general likelihood, not a guaranteed lab outcome.

Understanding Your Calculator Result

Results are generally grouped into broad categories rather than a single precise number:

• Higher likelihood of detection — your inputs align with scenarios where EtG is commonly still measurable at 100 ng/mL.
• Possible detection — substantial uncertainty — your inputs sit in a range where published research shows meaningful variation between individuals.
• Lower detection likelihood — your inputs align with scenarios where EtG has commonly fallen below 100 ng/mL, though individual results still vary.
• Low detection likelihood — your inputs are furthest from the profile associated with a positive result at this cutoff.

It's just as important to be clear about what these categories don't mean. "Low detection likelihood" describes a general pattern seen across research populations — it does not mean a guaranteed negative for you specifically. Category labels describe tendencies, not certainties, and that distinction is central to using the tool responsibly.

Why an EtG Calculator Cannot Guarantee a Negative Test

A calculator working from population-level research will always have limits when applied to one individual sample. Several factors explain why:

• Individual variability in metabolism, liver enzyme activity, and kidney function means two people with identical inputs can still produce different actual EtG concentrations.
• Urine concentration at the moment of collection is something no calculator can know in advance.
• Laboratory differences — cutoff, assay type, and confirmatory method — affect how a given concentration gets reported.
• Assay characteristics, including the sensitivity of the specific test used, vary between labs and providers.
• Timing uncertainty, since real-world recollection of exactly when drinking occurred is rarely precise to the hour.
• Uncertainty in reported alcohol amounts, since drink size, alcohol content, and pace all vary from what a standard-drink estimate assumes.
• Differences between population research and individual testing — published studies describe averages and ranges across groups of people, not a guarantee for any one person's next sample.

This is a limitation built into the nature of the science, not a flaw in any particular tool. Reading a result as one input into your understanding — alongside the calculator's disclaimers and, where the stakes are high, actual laboratory guidance — is the appropriate way to use it. For more on how estimate accuracy works generally, see how accurate is an EtG calculator.

EtG vs Blood Alcohol vs Breath Alcohol

The conceptual difference is straightforward: blood and breath alcohol tests measure alcohol that is currently affecting the body, so they answer "is this person impaired right now." Urine EtG measures a metabolic byproduct that lingers after the alcohol itself is gone, so it answers a different question — "did this person drink at some point recently." One test type can't be converted precisely into the other; a BAC reading at the time of drinking doesn't map to a specific EtG number hours or days later, because too many additional variables — dose, timing, individual metabolism, hydration — sit between the two measurements.

Cutoff selection isn't arbitrary — it reflects guidance that agencies overseeing alcohol testing have published specifically to address this trade-off. The Substance Abuse and Mental Health Services Administration (SAMHSA) has advised that a higher cutoff, such as 500 ng/mL, can help reduce false positives tied to incidental alcohol exposure, while acknowledging that stricter abstinence-monitoring programs often choose a lower, more sensitive threshold like 100 ng/mL. That guidance is a useful reminder that a cutoff represents a deliberate policy choice about sensitivity versus specificity — not a fixed scientific rule that applies identically to every testing context.

Frequently Asked Questions

What does 100 ng/mL mean on an EtG test? It's the concentration threshold — measured in nanograms of ethyl glucuronide per milliliter of urine — that a lab or program has set as the line between a negative and positive result. It's one of the more sensitive cutoffs in common use, meaning it can flag lighter or somewhat older drinking that a higher cutoff might miss.

How long can EtG remain detectable at 100 ng/mL? There's no single universal answer. Detection commonly extends from roughly a day up to several days depending on how much alcohol was consumed, individual metabolism, and urine concentration at collection. Lighter drinking generally clears sooner; heavier or repeated drinking can extend the window.

Is 100 ng/mL a low EtG cutoff? Yes, relative to more common thresholds like 300 or 500 ng/mL, 100 ng/mL is considered a low, sensitive cutoff. It's often used specifically because it's more likely to catch light or older drinking.

What is the difference between 100 and 500 ng/mL? The 100 ng/mL cutoff is more sensitive and catches a broader range of drinking scenarios, including lighter use, but is more susceptible to incidental, non-beverage exposure. The 500 ng/mL cutoff is less sensitive but tends to correspond more specifically to heavier or more recent drinking.

Does urine dilution affect EtG? Yes. Because EtG is reported as a concentration, a more diluted urine sample generally produces a lower ng/mL reading, independent of how much EtG the body has actually processed. Labs often check for signs of dilution separately.

Can an EtG calculator predict my laboratory result? No. A calculator applies research-informed, population-level relationships to give an educational estimate. It cannot know your real-time hydration, individual metabolism, or the specific assay a lab will use, all of which affect the actual number a lab reports.

Why can two people have different EtG results? Even with similar drinking histories, differences in body composition, timing, hydration, and individual metabolism can produce different measured concentrations — which is why EtG results should be read as individual data points, not as directly comparable between people.

Does drinking amount affect EtG detection? Yes, generally. Higher alcohol intake tends to produce a higher EtG peak and a longer window before concentration falls below a given cutoff, though the exact relationship varies by individual.

Does previous drinking affect EtG? It can. Drinking on more than one occasion within a short span, rather than a single isolated session, may extend how long EtG remains measurable, since earlier exposure hasn't necessarily fully cleared before additional alcohol is introduced.

Why do laboratories use different EtG cutoffs? Because programs weigh sensitivity against specificity differently. Some prioritize catching any possible drinking (favoring lower cutoffs like 100 ng/mL); others prioritize minimizing disputes over incidental exposure (favoring higher cutoffs like 500 ng/mL).

What does an EtG urine test measure? It measures ethyl glucuronide, a minor direct metabolite formed when the body processes ethanol. Because it persists in urine longer than alcohol itself, it's used to detect recent drinking rather than current impairment.

Is an EtG result the same as blood alcohol? No. Blood alcohol reflects active ethanol currently affecting the body, while EtG reflects a metabolic byproduct that remains measurable after the alcohol itself has cleared. The two are related but answer different questions and can't be converted directly into each other.

How accurate are EtG calculators? They're accurate as educational tools that apply published research to general scenarios, but they can't account for the real-time physiological variables — hydration, individual metabolism, assay specifics — that determine an actual lab result. They're best used to build understanding, not as a substitute for official testing guidance.