To calculate grams of alcohol in any drink, multiply the volume of the drink (in milliliters) by the ABV (as a decimal) and then by 0.789, which is the density of pure ethanol in grams per milliliter. That single formula works for any beverage, any size, anywhere in the world.
The Formula
The calculation has three ingredients: how much liquid you have, what percentage is alcohol, and how heavy that alcohol is. Pure ethanol weighs 0.789 grams per milliliter at room temperature, which is lighter than water. Here’s the formula:
Grams of alcohol = Volume (mL) × ABV (as a decimal) × 0.789
ABV stands for “alcohol by volume” and appears on virtually every beer, wine, and spirits label. A 5% beer has an ABV of 0.05 in the formula. A 40% whiskey is 0.40. The volume needs to be in milliliters. If you’re working with fluid ounces, multiply by 29.57 to convert (a 12 oz beer is about 355 mL).
Step-by-Step Examples
A 12 oz Beer at 5% ABV
Convert 12 fluid ounces to milliliters: 12 × 29.57 = 354.8 mL. Multiply by the ABV: 354.8 × 0.05 = 17.74 mL of pure alcohol. Multiply by the density: 17.74 × 0.789 = 14.0 grams. This matches the U.S. standard drink definition of 14 grams exactly, which is no coincidence. The standard drink was built around this common serving.
A 5 oz Glass of Wine at 13% ABV
Convert to milliliters: 5 × 29.57 = 147.9 mL. Multiply by ABV: 147.9 × 0.13 = 19.2 mL of pure alcohol. Multiply by density: 19.2 × 0.789 = 15.1 grams. That’s slightly more than one U.S. standard drink, which is worth knowing if you pour generously or if the wine is on the stronger side.
A 1.5 oz Shot of 40% Spirits
Convert: 1.5 × 29.57 = 44.4 mL. Multiply by ABV: 44.4 × 0.40 = 17.7 mL. Multiply by density: 17.7 × 0.789 = 14.0 grams. Again, right at 14 grams.
A 330 mL Craft Beer at 8% ABV
No conversion needed here since you already have milliliters. 330 × 0.08 = 26.4 mL of pure alcohol. Then 26.4 × 0.789 = 20.8 grams. That single can holds about 1.5 U.S. standard drinks.
ABV vs. ABW: Watch the Label
Some labels, particularly in certain U.S. states and on some beer packaging, list alcohol by weight (ABW) instead of alcohol by volume. Because alcohol is lighter than water, ABW is always a lower number than ABV for the same drink. To convert ABW to ABV, divide by 0.8 (or equivalently, multiply by 1.25). A beer labeled 4% ABW is actually 5% ABV. If you plug ABW directly into the formula without converting, you’ll undercount by about 20%.
Standard Drinks Vary by Country
Different countries define a “standard drink” with different gram amounts, which can create confusion if you’re reading health guidelines from another country. The U.S. sets its standard drink at 14 grams of pure alcohol. Canada uses 13.45 grams. Australia uses 10 grams. The UK uses an even smaller “unit” of just 8 grams (equal to 10 mL of pure alcohol), designed so that common drinks can be described in whole units rather than fractions. A pint of ordinary-strength beer in the UK comes to about 2 units, or 16 grams.
Knowing the gram count lets you translate between any of these systems. If a UK guideline recommends no more than 14 units per week, that’s 112 grams. The equivalent in U.S. standard drinks is 8 drinks per week.
Why Grams Matter for Health Tracking
Most international health research measures alcohol intake in grams rather than “drinks” because drink sizes and strengths vary so widely. The World Health Organization reports that the global average consumption among drinkers is about 27 grams of pure alcohol per day, roughly two standard glasses of wine or two regular beers. That level is associated with increased risk across a range of health conditions.
The gram count also feeds directly into estimating blood alcohol concentration. The Widmark equation, used in forensic and clinical settings, takes total grams consumed as its starting input and divides by body weight (in grams) multiplied by a distribution ratio (0.68 for men, 0.55 for women). Without an accurate gram figure, the estimate falls apart.
How Fast Your Body Clears Alcohol
A 70 kg (154 lb) adult metabolizes roughly 7 grams of alcohol per hour on average. That lines up neatly with “about one standard drink per hour,” though individual rates vary based on genetics, liver health, food intake, and body composition. Knowing the grams in your drink gives you a rough sense of timing. A 21-gram glass of wine, for example, takes about three hours to fully process rather than the single hour many people assume.
Quick Reference for Common Drinks
- 12 oz regular beer (5% ABV): 14 grams
- 12 oz strong craft beer (8% ABV): 22 grams
- 5 oz glass of wine (12% ABV): 14 grams
- 5 oz glass of wine (15% ABV): 17.5 grams
- 1.5 oz shot of spirits (40% ABV): 14 grams
- 16 oz pint of IPA (7% ABV): 26 grams
- 25 oz (750 mL) bottle of wine (13% ABV): 77 grams
Every one of these follows the same formula. Once you memorize volume × ABV × 0.789, you can calculate the alcohol content of anything with a label.