BAC Calculator: Peak % & Sober Time by Country

When you need a reality-check on “am I still over the limit?”

Not sure whether last night’s drinks could still put you above 0.05% (0.5‰) this morning—or whether you might drop below your selected limit in a few hours? This page explains exactly what the calculator is doing with your drink size, ABV, and timing, so you can spot the common input mistakes that skew BAC estimates.

The results are built around four ideas you can interpret quickly: current BAC (right now), peak BAC (highest point), legal time (first time at/under your chosen limit), and sober time (first time near zero).

Last Verified: December 2025

Educational estimate only. Do not use this to decide whether it is safe or legal to drive. If you drank alcohol, choose a sober ride.

Methodology (Widmark + time): what the math is actually using

The calculator converts every drink row into grams of ethanol, spreads those grams across the minutes you said you drank it, then subtracts a typical elimination rate over time. The key is that volume × ABV matters more than the drink “type.”

1) Drink → grams of ethanol

Ethanol (g) = Volume (ml) × (ABV ÷ 100) × 0.789

• 0.789 is ethanol density (g/ml). That is why “a bigger pour” moves BAC more than people expect.
• Preset drinks are just defaults; the Vol. and ABV fields are what count.

2) Ethanol grams → BAC estimate

BAC (%) ≈ (Ethanol grams ÷ (Body weight grams × r)) × 100 − (β × hours)

• r is the Widmark distribution ratio (estimated body-water fraction).
• β is the elimination rate used by the timeline (typical average: about 0.015% BAC per hour).
• Absorption is modeled across your drink duration (and a short delay). “Empty stomach” reduces the delay, so the peak arrives sooner.

Parameter guide (quick reference)

Worked example with interpretation (real numbers)

Scenario: 70 kg, male, three beers (355 ml each) at 5% ABV over ~1 hour.

1. Total volume ≈ 3 × 355 ml = 1,065 ml
2. Ethanol grams ≈ 1,065 × 0.05 × 0.789 ≈ 42 g
3. Body-water mass ≈ 70,000 g × 0.68 ≈ 47,600 g
4. Estimated BAC before elimination ≈ (42 ÷ 47,600) × 100 ≈ 0.088%
5. After ~1 hour of elimination: 0.088 − 0.015 ≈ 0.073%

Interpretation: the same drinks can be below one legal limit and above another. That is why “country limit” (or “Custom”) matters.

You Can Try (to understand the curve)

• Two beers spaced out: Add Beer twice (Qty 1 each), set the second start time ~60 minutes later, and use 25–40 min duration for each. Expect two smaller bumps instead of one tall spike.
• Wine then cocktail: Enter Wine (150 ml, 12%) and a Cocktail (250 ml, 15%) ~45 minutes later. Expect a later, higher peak because more ethanol grams arrive while BAC is still elevated.
• Empty stomach vs. not: Run the same drinks twice with the toggle on/off. You’ll usually see the peak happen sooner (and sometimes slightly higher) when “empty stomach” is on.
• Tall can reality check: Use Custom for a 16 oz beer at 6.5%. Compare it to a standard 12 oz at 5%—the tall can contains roughly ~1.7× the ethanol, so the curve should rise noticeably more.

💡 Tips for Better Estimates (math/logic)

• ABV is a percent: Enter 5 for 5% (not 0.05). A common error is mixing percent with fraction.
• Total alcohol depends on ethanol grams: The calculator treats alcohol as Volume × ABV. If your drink is “stronger” or “bigger,” it’s not a small tweak—your curve can shift a lot.
• Duration controls the peak timing: The same total alcohol spread over 10 min vs. 40 min can change the curve shape (how sharp the rise is), even if the final total grams are identical.
• Order matters for time: Enter drinks in the order you started them. If you mix the order, the timeline may show a different peak placement than your real session.
• Don’t “tune” the elimination rate: The model uses a fixed average elimination (β). If your goal is safety planning, assume your real clearance could be slower than average.

🧩 What Actually Changes the BAC Number (in the model)

• Ethanol amount (grams): Determined by drink volume × ABV. This is the biggest driver of the result.
• Distribution ratio (r): A proxy for how alcohol dilutes in body water. Different selections change dilution, not the alcohol you consumed.
• Body weight: More mass (in this model) means the same ethanol grams are spread out more, lowering the peak.
• Timing & pacing: Start times and durations shape when ethanol is added, producing one peak, multiple peaks, or a plateau.
• Absorption assumption: The “empty stomach” toggle primarily shifts how quickly the rise happens (peak arrives earlier).
• Elimination rate (β): The decline is modeled as a steady reduction per hour. Real-world rates vary, so treat the curve as an estimate.

Important: things like coffee, showers, or “feeling fine” may change perceived alertness, but they do not change ethanol grams or the model’s elimination slope.

🥤 What Is a “Standard Drink” (quick input check)

A “standard drink” is a shorthand for a typical dose of pure alcohol. Your real servings may be larger—use Custom to match the label or your pour.

Common mistake: treating a pint as “one beer.” A pint is larger than 12 oz, so ethanol grams are higher even at the same ABV.

❌ Common BAC Myths — What the math says

• “Coffee sobers you up.” Coffee may increase alertness, but it doesn’t change ethanol grams or the elimination rate (β), so the BAC curve doesn’t drop faster.
• “A cold shower lowers BAC.” Temperature doesn’t remove ethanol from blood. The model’s decline comes from elimination over time, not sweating or shock.
• “Eating after drinking lowers BAC immediately.” Food can slow absorption before alcohol is absorbed, but once ethanol is in the blood, BAC falls mainly through elimination over time.
• “Beer is safer than liquor.” The calculator doesn’t care about drink names—only total ethanol grams delivered over time.

✅ Safety Notes (short)

• Legal limits vary and may be lower for novice or professional drivers—treat the country selector as a quick reference, not legal advice.
• Impairment can occur below the limit. “Under the limit” is not a guarantee of safe driving.
• If in doubt, don’t drive. Use a sober ride or wait longer than the estimate.

Infographic & visual guide: reading the BAC chart without guessing

What the curve shape usually means

• Sharp spike → a strong drink finished quickly (high ABV, short duration).
• Plateau → your drinking pace roughly matches elimination for a while.
• Second peak → a later drink overlaps with the decline from earlier drinks.

Marker legend (matches the vertical lines)

• 🟨 Now: the point in time you are checking.
• 🟥 Peak: highest estimated BAC on the timeline.
• 🟧 Legal time: first time BAC returns to/under your selected limit (if it happens within the simulated window).
• 🟩 Sober time: first time near 0.00% (very low threshold) is reached (if it happens within the simulated window).

Two timing edge cases that change the curve

• Midnight rollover: if a later row has an earlier clock time than the previous row, it is treated as the next day (shown as +1d / +2d).
• Empty stomach: the rise shifts earlier. The total ethanol grams do not change, but the peak can arrive sooner.

Practical use cases (and what to do with the output)

• Planning transport: compare your current BAC to a strict limit (e.g., 0.02%) vs a general limit (e.g., 0.05%).
• Checking “strong pours”: enter a custom ABV for craft beer or cocktails where 5% / 15% presets are too low.
• Seeing pacing effects: keep the same drinks but increase each drink’s duration to model slower sipping (later, lower peak).
• Learning the units: avoid the percent vs promille trap (0.5‰ equals 0.05%).

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Math-specific tips (these prevent the biggest BAC errors)

Common mistakes

• ABV entered as a fraction: typing 0.05 instead of 5 changes ethanol grams by 100×.
• Percent vs promille confusion: 0.05% equals 0.5‰ (not 0.05‰). Many EU limits are stated in ‰.
• “One beer” isn’t one number: a 500 ml beer at 6.5% contains much more ethanol than 330 ml at 5%.
• Pint/cup assumptions: “pint” sizes differ by country; treat them as approximations and adjust volume if needed.
• Unrealistic drinking duration: finishing everything in 1–2 minutes forces an unrealistically steep spike.

Quick consistency checks

• Check ethanol grams: higher ABV or larger volume should always increase peak BAC.
• Check pacing: spreading the same ethanol over more minutes should push the peak later and often lower.
• Check the limit: if your local rule is stricter than the dropdown preset, use Custom and enter the exact number.

Standard drink quick reference (use this to sanity-check your inputs)

“Standard drink” definitions vary by country. The table below uses a common reference point: servings that land near ~14 g of pure alcohol. Use Custom whenever your pour is larger or stronger than the default.

These are approximations. Labels, pours, and glass sizes vary.

Typical effects by BAC range (why “under the limit” can still feel impaired)

This table is informational and not medical advice.

Legal BAC limits: use presets carefully (UK/Germany edge case included)

The dropdown is a convenience. Some places have different limits by region or driver type (novice, commercial, professional). If your exact limit differs from the preset, choose Custom and enter the correct value for your situation.

• UK: limits differ by region. If your jurisdiction uses 0.08% and the preset is lower, use Custom.
• Germany: 0.05% is a common general threshold, but some drivers (novice/under-21) are subject to stricter rules.
• Zero-tolerance: if your rule is effectively 0.00%, “legal time” is essentially “sober time.”

This table is a quick reference, not legal advice. Laws and categories change; always verify with official local sources.

FAQ (tool-specific)