BAC by Weight: How Much Can You Drink at Different Body Weights?
Alex Harmon · Updated June 2026 · Reviewed for accuracy
Body weight is one of the two most important variables in determining your blood alcohol concentration — the other being sex. A 50kg woman and a 100kg man can drink the same number of drinks and end up with dramatically different BAC levels. Understanding the science behind why this happens, and the specific numbers involved, is critical if you want to make accurate judgments about your own sobriety and safety.
Why Weight Changes Your BAC
When you drink alcohol, it does not stay in your stomach — it absorbs quickly into the bloodstream and then distributes throughout the water in your body. The key phrase is "the water in your body." Alcohol is water-soluble, and it distributes through your total body water (TBW) — not just your blood. The more body water you have, the more diluted a given amount of alcohol becomes, and therefore the lower your BAC.
Heavier people generally have more total body water in absolute terms. A 100kg man might have 57 litres of total body water, while a 60kg man might have 34 litres. Pour the same amount of alcohol into a larger container and you get a lower concentration — this is the fundamental reason why weight matters so much for BAC.
This relationship is captured mathematically in the Widmark formula, the basis of virtually all BAC calculators:
BAC = (Alcohol in grams) ÷ (Body weight in kg × r) × 100
The "r" value in this formula is the Widmark distribution factor — a number that represents what fraction of your body weight is body water. For the average adult male, r = 0.68. For the average adult female, r = 0.55. These averages reflect the fact that women generally have a higher body fat percentage than men (fat holds very little water), which means proportionally less body water to dilute alcohol.
Estimated BAC by Weight After 1 Hour
The tables below show estimated BAC levels by body weight after consuming 1–6 standard drinks over one hour, after subtracting one hour of metabolism (approximately 0.015%). Each "standard drink" is assumed to contain 14 grams of pure alcohol — roughly equivalent to a 355ml regular beer (5%), a 148ml glass of wine (12%), or a 44ml shot of spirits (40%).
Male (r = 0.68)
| Drinks | 50 kg | 60 kg | 70 kg | 80 kg | 90 kg | 100 kg |
|---|---|---|---|---|---|---|
| 1 | 0.026% | 0.019% | 0.012% | 0.007% | 0.002% | 0.000% |
| 2 | 0.056% | 0.043% | 0.033% | 0.026% | 0.020% | 0.015% |
| 3 | 0.085% | 0.068% | 0.055% | 0.044% | 0.037% | 0.030% |
| 4 | 0.115% | 0.093% | 0.076% | 0.063% | 0.053% | 0.045% |
| 5 | 0.144% | 0.117% | 0.097% | 0.082% | 0.069% | 0.059% |
| 6 | 0.173% | 0.141% | 0.118% | 0.100% | 0.086% | 0.074% |
Female (r = 0.55)
| Drinks | 50 kg | 60 kg | 70 kg | 80 kg | 90 kg | 100 kg |
|---|---|---|---|---|---|---|
| 1 | 0.036% | 0.027% | 0.021% | 0.017% | 0.013% | 0.011% |
| 2 | 0.072% | 0.057% | 0.046% | 0.038% | 0.031% | 0.026% |
| 3 | 0.108% | 0.087% | 0.072% | 0.060% | 0.051% | 0.044% |
| 4 | 0.144% | 0.117% | 0.097% | 0.082% | 0.070% | 0.061% |
| 5 | 0.181% | 0.148% | 0.123% | 0.104% | 0.089% | 0.078% |
| 6 | 0.217% | 0.178% | 0.149% | 0.126% | 0.108% | 0.095% |
Green = below 0.05% · Amber = 0.05–0.079% · Red = 0.08% and above (at or above typical legal driving limit). Values are estimates only — use the BAC Calculator for precise results.
Key Takeaway: The Difference Is Dramatic
Look at 3 drinks in the tables above. A 50kg woman reaches an estimated 0.108% BAC — well above the 0.08% legal limit in most countries. A 100kg man at the same 3 drinks sits at roughly 0.030% — less than half the legal limit. That is the same number of drinks producing more than three times the BAC. This disparity is why statements like "I only had three drinks" are meaningless without knowing who said them.
The takeaway is not that heavier people can drink freely. It is that weight is a critical variable, and smaller, lighter people reach dangerous BAC levels far more quickly than they may expect.
Weight Matters — But It's Not the Whole Story
The r Factor: Body Composition
The Widmark r value (0.68 for males, 0.55 for females) is an average, but real individuals vary significantly — from approximately 0.45 to 0.85 depending on body composition. Muscle tissue contains roughly 75% water by weight. Fat tissue contains only about 10% water. Two people of identical weight — one muscular, one with higher body fat — will have different BAC levels after the same drinks, because the muscular person has more total body water to dilute the alcohol. This means the tables above are estimates; a highly muscular person will have a lower BAC than shown, and a person with high body fat percentage may have a higher BAC than shown.
Age
Liver efficiency tends to decline with age. Older adults metabolize alcohol more slowly than younger adults, meaning the same BAC persists longer. Additionally, older adults generally have lower total body water as a proportion of body weight, which further raises BAC relative to what younger people experience at the same weight and drink count.
The One Thing Weight Cannot Change
No matter how much you weigh, your liver metabolizes alcohol at roughly the same rate: approximately 0.015% BAC per hour. A heavier person who starts at a lower BAC may reach sobriety faster in absolute time, but their liver is not processing alcohol any more efficiently. There is no shortcut. Weight gives you a lower starting point — not a faster exit.
Drinks to Reach 0.08% by Weight
| Body Weight | Male (approx. drinks) | Female (approx. drinks) |
|---|---|---|
| 50 kg | 3 | 2 |
| 60 kg | 3–4 | 2–3 |
| 70 kg | 4 | 3 |
| 80 kg | 5 | 3–4 |
| 90 kg | 5–6 | 4 |
| 100 kg | 6+ | 4–5 |
Approximate number of standard drinks consumed over 1 hour to reach 0.08% BAC. These are estimates — individual variation is significant. Always use a calculator for decisions that matter.
These tables give you a framework, but the most accurate estimate of your current BAC accounts for your exact weight, sex, number of drinks, drink strength, and time elapsed. Use our BAC Calculator to run the numbers for your specific situation before making any driving decision.
Frequently Asked Questions
Does body weight affect BAC?
Yes, significantly. Alcohol distributes through total body water, and heavier people have more of it. The same amount of alcohol spread across a larger volume of body water produces a lower blood alcohol concentration. A 100kg man can consume roughly double the drinks of a 50kg woman before reaching the same BAC. However, weight does not change how fast the liver clears alcohol — that rate is approximately 0.015% per hour for all adults.
Do heavier people sober up faster?
No. Liver alcohol metabolism runs at approximately 0.015% BAC per hour regardless of body weight. A heavier person starts at a lower BAC after the same drinks, so they may reach legal sobriety faster in that sense — but their liver is not processing alcohol any more quickly. The time to go from a given BAC to zero is essentially the same for everyone.
Does muscle vs fat matter for alcohol metabolism?
Yes. Muscle tissue contains significantly more water than fat tissue. A muscular person has more total body water to dilute alcohol compared to someone of the same weight with higher body fat. This is part of why the Widmark r factor varies between individuals — it is not a fixed value but reflects real body composition differences. Muscular people will generally have a lower BAC than the table estimates suggest; people with higher body fat may be higher.