Understanding the BAC Chart
Erik Widmark built this formula in 1932, and forensic toxicologists worldwide still rely on it because nobody has produced anything broadly better in ninety-plus years of trying. The chart above plugs your drink count and body weight into that same equation to estimate BAC after one hour of drinking with moderate food intake — which makes it a quick reference rather than a clinical measurement, but a useful one.
The way to read it is dead simple: find your body weight across the top row, look down that column, and each row shows what happens as drinks stack up. We color-coded the cells because squinting at decimals in a bar is not realistic — green means you are likely below the point where most people notice anything, yellow means impairment is creeping in, orange means you have crossed the 0.08% legal line, and red means you are in genuinely dangerous territory.
Why Body Weight Matters
Three drinks barely move the needle at 220 pounds but can push a 130-pound person past the legal limit — the chart makes that painfully obvious. Alcohol dilutes through body water, and bigger bodies simply carry more of it.
Keep in mind that the chart tracks body weight, not muscle mass or body fat percentage. Two people at the same weight but different body compositions will have slightly different actual BACs, because fat tissue holds less water than muscle.
Male vs Female Differences
The toggle at the top flips between male and female charts. Women generally reach higher BAC levels than men at the same weight and drink count — this isn't about tolerance or drinking experience, it's a physiological difference. Women average about 55% body water compared to 68% for men, so the same amount of alcohol concentrates more in a woman's bloodstream.
The Widmark formula handles this through the "r" factor: 0.68 for biological males and 0.55 for biological females. Flip the toggle and every cell in the chart updates instantly with the appropriate factor.
What Counts as One Drink
NIAAA pegged one standard drink at 14 grams of pure alcohol — which translates to a 12-ounce can of regular beer at 5% ABV, a number most people get right because cans are pre-measured. Wine is where it falls apart: the official pour is 5 ounces at 12% ABV, but almost nobody pours that little at home. Spirits sit at 1.5 ounces at 40% ABV, the size of a single jigger — and most home bartenders eyeball at least double that. Each row in the chart adds one of those standard units, and the mismatch between what NIAAA counts and what actually ends up in your glass is the single biggest source of BAC miscalculation.
NIAAA's drink size guide exists for a reason — most people have never measured what they actually pour and the mismatch is enormous. At home, a typical wine glass gets filled to 7 or 8 ounces rather than the standard 5, which alone turns one drink into 1.5. A pint of craft IPA at 7.5% ABV works out to two standard drinks, not one. A Long Island Iced Tea packs 3 to 4 standard drinks into what looks like a single cocktail. If you are unsure how your drinks translate, try our Standard Drinks Calculator.
The 0.08% Legal Limit
NHTSA's crash data put the inflection point right at that 0.08% line — the legal limit in all 50 states except Utah at 0.05% — where crash risk jumps roughly fourfold compared to sober driving. That is the dashed line on the chart where cells shift from yellow to orange, and it marks the threshold where coordination measurably deteriorates and reaction times slow enough to matter at highway speeds.
NHTSA's case-control crash risk study measured drivers at just 0.05% BAC as roughly twice as likely to crash compared to sober ones — well below the 0.08% legal line — even though most people at that level genuinely feel fine. That disconnect between subjective confidence and measured impairment is exactly why dozens of countries set their legal limits at 0.05% or lower, and why the yellow zone on this chart deserves more respect than the green light it might seem like.
Factors the Chart Cannot Show
This chart assumes one hour of drinking and moderate food intake. Your actual BAC depends on additional factors:
- Time: Your liver eliminates alcohol at roughly 0.015% per hour. Drinking the same amount over three hours produces a lower peak BAC than consuming it in one hour.
- Food: Drinking on an empty stomach means faster absorption and a higher peak BAC. A full meal can reduce peak BAC significantly.
- Medications: Many common medications interact with alcohol, including antihistamines, antidepressants, and pain relievers.
- Individual variation: Metabolism, liver health, genetics, hydration, and fatigue all influence your actual BAC.
For a more personalized estimate that accounts for time and food intake, use our BAC Calculator on the main page.
How to Use This Chart Responsibly
We built this as an educational reference, not a green light to get behind the wheel. The Widmark formula uses population averages for metabolism and body water — your actual BAC depends on liver health, medications, hydration, genetics, and a dozen other variables the equation cannot see. If the chart puts you anywhere near the orange zone, the smart assumption is that your real number could be higher.
If you have had a few drinks and you are sitting there doing the math on whether you can drive — that hesitation is the answer. Call a rideshare, grab a cab, or hand the keys to a sober friend. A $25 ride home costs less than the $10,000-plus average for a first-offense DUI, and infinitely less than the alternative nobody wants to think about. Check our state-by-state legal limits for the specific laws and penalties where you live.