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Blood Alcohol Chart by Weight: How Body Weight Changes Your BAC

Updated April 2026 · 10 min read

Body weight is the second most important variable in your blood alcohol level, right after how many drinks you have had — and it moves the number around more than most people realize. A 140-pound woman and a 220-pound man drinking the same three beers will land roughly 80% apart on the BAC scale, which is the difference between feeling loose and being legally impaired. This page lays out the estimated BAC for common weights and drink counts, explains why the math works the way it does, and points at what the chart cannot see.

The tables below use the Widmark formula with population-average body water fractions — 0.68 for men and 0.55 for women — and assume an empty stomach, which produces the highest realistic peak. Food in the stomach knocks about 15 to 35 percent off those values, depending on how much you have eaten. Time since your last drink brings the numbers down at roughly 0.015% per hour. Both factors are covered in the sections below.

BAC Chart by Weight — Men

Values assume empty stomach, standard drinks of 14 grams ethanol each, and peak BAC before the liver has cleared much of the dose. Zones follow the BAC Levels color system — green under 0.05%, yellow up to 0.08%, orange through 0.15%, red above that.

Weight 1 drink 2 drinks 3 drinks 4 drinks 5 drinks
120 lb 0.038 0.076 0.113 0.151 0.189
140 lb 0.032 0.065 0.097 0.130 0.162
160 lb 0.028 0.057 0.085 0.113 0.142
180 lb 0.025 0.050 0.076 0.101 0.126
200 lb 0.023 0.045 0.068 0.091 0.113
220 lb 0.021 0.041 0.062 0.083 0.103

BAC Chart by Weight — Women

Same assumptions and same color system. The numbers run roughly 20 to 25 percent higher than the male chart at matched weights because of the body water gap covered below.

Weight 1 drink 2 drinks 3 drinks 4 drinks 5 drinks
100 lb 0.056 0.112 0.168 0.225 0.281
120 lb 0.047 0.094 0.140 0.187 0.234
140 lb 0.040 0.080 0.120 0.160 0.200
160 lb 0.035 0.070 0.105 0.140 0.175
180 lb 0.031 0.062 0.094 0.125 0.156
200 lb 0.028 0.056 0.084 0.112 0.140

For an interactive version with finer weight increments and time-based elimination, the BAC Chart tool lets you move through weights and drinks continuously and flips between male and female rows on a single control.

The Widmark Formula Behind the Numbers

The math behind these tables comes from a 1932 paper by Erik Widmark in the German forensic toxicology literature, and the fact that nobody has replaced it in ninety-plus years of trying is a quiet compliment to the original work. The equation is short: BAC equals alcohol grams times 100, divided by body weight in grams times r. What matters is that r factor, because alcohol distributes through body water rather than through muscle or fat — and the r value is basically your body water proportion in disguise. Widmark published 0.68 for men and 0.55 for women, and those two numbers do most of the heavy lifting in the tables above.

The constants matter because they are doing most of the work in the chart. Alcohol grams per standard drink is 14 by the NIAAA definition, body weight gets converted to grams, and r falls between 0.55 and 0.68 for most adults. That puts the entire arithmetic of "how high does a drink push my BAC" on two numbers: how much you weigh, and which r value matches your body. Age, height, and body composition shift r at the margins, but the population averages in this chart cover most people within plus or minus 10%.

Body Water and the Watson Formula

The Watson 1980 paper in the American Journal of Clinical Nutrition — Total Body Water Volumes for Adult Males and Females Estimated from Simple Anthropometric Measurements — set the modern standard for estimating how much of a person's body is water. The headline result is that adult men average around 58 to 60 percent body water and adult women average around 48 to 50 percent. Those fractions are where the Widmark r values come from, because r is literally the body water proportion adjusted by the slight density difference between water and whole blood.

The male-female gap is not a moral or behavioral claim, it is a plumbing claim. Women's bodies carry a higher proportion of adipose tissue by default, and adipose tissue holds about 10 to 20 percent water compared to the 75 percent in lean muscle. The same 3 drinks dilute into a smaller water reservoir in a 140-pound woman than they do in a 140-pound man, which is why every female row in the chart above sits higher than its male equivalent. The Watson formulas also show that age pushes body water down in both sexes — older adults tend to land above the chart value for the same weight, and younger adults tend to land slightly below.

What NIAAA Counts as One Drink

NIAAA's standard drink definition is the single biggest source of BAC miscalculation in the real world. Fourteen grams of pure ethanol translates to a 12-ounce can of regular beer at 5% ABV, a 5-ounce pour of wine at 12% ABV, or a 1.5-ounce shot of 40% ABV distilled spirits. Cans hit the spec reliably because they are pre-measured. Nothing else in your house does.

A typical home wine pour lands between 7 and 8 ounces — which turns one drink into 1.5 on the chart above. A pint of craft IPA at 7.5% ABV works out to about two standard drinks in a single glass, not one. A margarita with a generous bartender can easily carry two and a half standards, and a Long Island Iced Tea runs three to four standards in one glass. If you are counting glasses instead of standards, the chart is underreading your real BAC by 50% or more. The standard drinks calculator converts specific drinks into standards so the chart math lines up with what is actually in your glass.

How Fast the Numbers Come Down

Ethanol metabolism in most healthy adults runs at roughly 0.015% BAC per hour, which is a zero-order process — the rate does not change with how much alcohol is in your system. A peak of 0.10% takes about six and a half hours to clear to zero. A peak of 0.15% takes about ten hours. Heavy chronic drinkers sometimes metabolize slightly faster because of enzyme induction, and people with liver damage metabolize slower, but the variation is small compared to the rock-solid 0.015% baseline.

None of the popular tricks to speed up that rate actually work. Coffee, cold showers, greasy food after drinking, exercise, water, vomiting past the first 20 minutes — all zero effect on the clearance rate. The sobering up guide walks through the research on each myth with real citations. For the chart above, the practical takeaway is that you can subtract 0.015% for every hour since your last drink to get a rough current estimate from a peak value.

The 0.08% Legal Line and What the Data Says

The Blomberg NHTSA case-control study, DOT HS 812 355 — titled Crash Risk of Alcohol Impaired Driving — measured the odds of a crash against sober drivers at real-world BAC levels. At 0.05% BAC the relative risk was about 2.07 times sober. At 0.08% it was 3.98 times sober, almost quadruple. Those numbers are unadjusted for age and sex but hold up after adjustment. That fourfold jump is why 0.08% became the legal threshold in 49 states, with Utah at 0.05% representing what the data arguably supports as a better public-health threshold.

The yellow zones on the chart above are where most people feel fine but the crash risk has already doubled. A 140-pound woman at two drinks is already at 0.08%, with a 140-pound man at that same 0.08% needing about four drinks to get there. The math does not care how confident either of them feel behind the wheel — subjective assessment at 0.05% to 0.08% is not reliable, and that gap between "feeling okay" and "being twice as likely to crash" is the most dangerous window the chart shows.

Factors the Chart Cannot See

The numbers in the tables above are population-average estimates for an empty stomach, no medications, no unusual hydration state, and typical body composition for the given weight. Real BAC moves around that average for reasons the equation does not capture.

Using the Chart Responsibly

The whole purpose of this reference is planning, not permission. Figure out how many drinks you can fit before needing a rideshare, whether the wait before driving is two hours or four, whether a lighter friend has quietly crossed a line you did not.

The chart is not a breathalyzer, and it is not an excuse. When you are sitting there doing the math on whether you can drive, the hesitation itself is the answer.

For live numbers with time and food accounted for, the BAC Calculator on the homepage runs the full equation with your specific inputs. For state-specific laws on what BAC will get you charged and what the penalties look like, the legal limits by state reference covers all 50 plus commercial drivers and under-21 thresholds. If the timing is tight, the sober calculator tells you the honest hours until you drop to zero from any starting point.

Sources

Frequently Asked Questions

How many drinks before a 140-lb woman reaches 0.08%?
Roughly two standard drinks on an empty stomach. The Widmark math at 140 pounds with a 0.55 factor puts two drinks around 0.080% and three drinks around 0.120%. That is why the second drink is the one that crosses the legal line for most lighter women, not the third or the fourth. Food slows absorption and shifts the peak lower, but it does not change the total amount of alcohol clearing the liver.
How many drinks before a 200-lb man reaches 0.08%?
About four standard drinks on an empty stomach. The 200-pound male row in the chart shows roughly 0.045% after two drinks, 0.068% after three, and 0.091% after four. That fourth drink is the one that puts the average 200-pound man across 0.08%. Food, time between drinks, and individual metabolism all move the real peak around that estimate by 10-20%.
Why does the female chart show higher numbers at the same weight?
Women average around 49% total body water compared to about 58% for men, based on the Watson 1980 anthropometric formulas. Alcohol distributes through body water, so a smaller water compartment produces a higher concentration for the same alcohol dose. The Widmark factor captures that gap — 0.55 for women, 0.68 for men — and the 24% difference in those factors is why the cells in the female chart run roughly 20 to 25 percent above the male chart at the same weight.
Does the chart apply to drinks at home or only to bars?
It applies to the standard drink definition, which is 14 grams of pure ethanol. A bar pour and a home pour are rarely the same size. A home wine glass usually holds 7 to 8 ounces instead of the 5 ounces NIAAA counts as one drink, a craft IPA at 7.5% ABV is closer to two standards than one, and a Long Island Iced Tea packs three to four standard drinks into a single glass. The chart rows assume you are counting standards, not glasses.
How long before the BAC in this chart drops back to zero?
The liver clears about 0.015% BAC per hour. A peak of 0.08% takes roughly five to six hours to drop to zero. A peak of 0.12% takes about eight hours. The math is linear: divide peak BAC by 0.015 and the answer is hours to sober. There is no way to accelerate that clearance — coffee, cold showers, and food do not change the rate the liver processes alcohol.
Does muscle mass or body fat change the numbers?
Yes, and the chart cannot see it. Alcohol distributes through body water, and muscle tissue holds roughly 75% water while fat tissue holds about 10-20%. Two people at 180 pounds will hit different peak BACs if one is lean and the other is higher body fat, with the leaner person usually landing a little below the chart value and the higher-fat person a little above. The chart uses average body composition for each weight, which works for most people within plus or minus 10%.
Is this chart accurate enough to decide whether to drive?
No chart is. The Widmark formula is a population average, and your real BAC depends on liver health, medications, hydration, food timing, genetics, and a dozen other variables the equation cannot measure. The chart is a rough guide for planning, not a breathalyzer. If the chart puts you anywhere near 0.05% the honest assumption is that your real number could be meaningfully higher — and at 0.08% you should already have found another way home.
Why does the chart start at 100 lb for women and 120 lb for men?
Those are common lower bounds for adult body weight in most reference tables. The Widmark formula is linear in weight, so extrapolating down to 80 pounds or up to 300 pounds works mathematically — just divide or scale the values you see. A 100-pound woman and a 300-pound man will show up in the same chart math even though the real-world physiology is pulling harder in both directions. For very low or very high weights the chart becomes a rougher guide, and the individual variation gets wider.