Alcohol Unit Calculator – From Drinks to Units, Grams and BAC
Different drinks contain very different amounts of pure alcohol. A small glass of strong spirits can contain as much alcohol as a large glass of wine or a bottle of beer. The Alcohol Unit Calculator on MyTimeCalculator converts common drink sizes and strengths into alcohol units, grams of pure alcohol, approximate standard drinks and a rough blood alcohol concentration (BAC) estimate.
This page uses a widely used definition of an alcohol unit and standard conversion formulas. It is designed for education and basic planning only. It does not give medical advice and cannot tell you whether it is safe to drive, work or operate machinery.
Key Formulas Used by the Alcohol Unit Calculator
The calculator is built around a few simple formulas.
1. Volume conversion to milliliters
All calculations are based on the drink volume in milliliters (ml). For each input, the calculator converts the amount into ml using preset factors:
- Liters: ml = liters × 1000
- US fluid ounces: ml ≈ ounces × 29.5735
- UK pint: ml ≈ pints × 568
- US pint: ml ≈ pints × 473
- Preset cans: ml = count × preset volume (330, 355, 440 or 500 ml)
- Preset wine glasses: ml = count × glass size (150, 175 or 200 ml)
- Preset shots: ml = count × shot size (30 or 44 ml)
2. Alcohol units from volume and ABV
A common definition of an alcohol unit is that one unit contains 10 ml of pure ethanol. The calculator uses the formula
Units = (Volume in ml × ABV%) ÷ 1000
For example:
- 500 ml of beer at 5% ABV: Units = (500 × 5) ÷ 1000 = 2.5 units
- 175 ml of wine at 12% ABV: Units = (175 × 12) ÷ 1000 = 2.1 units
- 25 ml shot at 40% ABV: Units = (25 × 40) ÷ 1000 = 1.0 unit
3. Grams of pure alcohol from units
The density of ethanol is roughly 0.8 g/ml. With one unit defined as 10 ml of pure alcohol, one unit contains about 8 grams of ethanol. The conversion is
Grams = Units × 8
Reversing this gives
Units = Grams ÷ 8
4. Approximate standard drinks
The definition of a standard drink varies by country. Some examples:
- 10 g of pure alcohol in some countries
- 14 g of pure alcohol in several guidelines
The calculator reports the equivalent number of standard drinks under both definitions:
- Standard drinks (10 g) = Grams ÷ 10
- Standard drinks (14 g) = Grams ÷ 14
5. Widmark-style BAC estimate
The BAC tab uses a simplified version of the Widmark equation to give a rough estimate of blood alcohol concentration. Let
- A = grams of pure alcohol consumed
- W = body weight in kilograms
- r = body water distribution factor (about 0.68 for men, 0.55 for women)
- β = average elimination rate per hour (often approximated as 0.015 g/dL per hour)
- t = hours since drinking started
A rough peak BAC in g/dL is calculated as
BACpeak ≈ (A ÷ (r × W × 10))
The factor of 10 converts kilograms into deciliters of body water in a simplified way. To account for metabolism over time, the calculator subtracts an elimination term:
BACtime ≈ max(0, BACpeak − β × t)
The calculator uses units to grams conversion (A = Units × 8) and then applies these formulas. Because individual metabolism differs, the output is only an approximation and must not be used for legal or safety decisions.
How to Use Each Tab of the Alcohol Unit Calculator
Tab 1: Single Drink Units
In the single drink tab you enter:
- The amount (volume or number of preset drinks)
- The volume unit or preset (ml, L, oz, pints, cans, wine glasses, shots)
- The ABV percentage
The calculator converts your input into ml, applies Units = (ml × ABV%) ÷ 1000 and shows:
- Total drink volume in ml
- Alcohol units
- Pure alcohol grams
- Standard drinks based on 10 g and 14 g definitions
Tab 2: Multiple Drinks
The multiple drinks tab lets you combine up to five different drink types. For each row you enter:
- Amount (volume or count)
- Unit or preset
- ABV percentage
For each drink type the calculator converts volume to ml, applies the unit formula and sums:
- Total volume in ml across all drinks
- Total alcohol units
- Total grams of pure alcohol
- Total standard drinks at 10 g and 14 g
You can copy the total units number directly into the BAC or weekly intake tabs.
Tab 3: Units, Grams and Standard Drinks
This tab does not require volume or ABV. Instead you can supply either:
- Alcohol units, which convert to grams with Grams = Units × 8, or
- Grams of pure alcohol, which convert to units with Units = Grams ÷ 8
The calculator then reports:
- Units
- Grams of pure alcohol
- Approximate standard drinks if one drink is 10 g
- Approximate standard drinks if one drink is 14 g
Tab 4: BAC Estimate
In the BAC tab you provide:
- Your sex (used to set r)
- Your body weight
- Total alcohol units consumed
- Hours since drinking started
The calculator first converts units to grams (A = Units × 8), then applies the Widmark-style formula for peak BAC and subtracts β × t to estimate BAC at the given time:
- BACpeak ≈ A ÷ (r × W × 10)
- BACtime ≈ max(0, BACpeak − β × t)
It also shows a rough interpretation band such as very low, moderate or high BAC levels. This information is only approximate and must not be used to decide whether you are safe or legal to drive.
Tab 5: Weekly Intake
The weekly intake tab helps you log consumption over seven days. You enter units for Monday through Sunday and set a reference weekly limit (for example, 14 units). The calculator then provides:
- Total weekly units
- Average units per day
- The limit you entered
- Whether your total is below, near or above the reference limit
Because different countries and organizations define low-risk guidelines differently, you can adjust the limit value to match your local recommendations.
Tab 6: Guidelines and Intake Categories
The last tab summarizes how your weekly units compare to the reference limit you choose. It classifies intake into levels such as very low, within limit, above limit or far above limit based on the ratio of weekly units to the reference threshold. It also provides a small table of example patterns such as low or no use, within low-risk guidelines, above guidelines and heavy or high-risk use.
Important Notes and Limitations
- Guidelines about low-risk drinking vary by country and can change over time.
- Individual responses to alcohol differ due to body composition, health conditions, medications, sleep, food intake and many other factors.
- BAC estimates are approximate and should never be used to make legal or safety decisions.
- This calculator does not account for rapid or binge drinking, nor does it model detailed absorption and elimination curves.
- For personalized advice about alcohol and health, consult a qualified health professional and follow your local regulations and official guidance.
This Alcohol Unit Calculator is best used as a learning tool to better understand how different drinks, sizes and strengths combine into total alcohol intake over a day or week.
Alcohol Units FAQs
Frequently Asked Questions About Alcohol Units
Quick answers to help you interpret units, grams, standard drinks and BAC estimates.
No. An alcohol unit is often defined as 10 ml of pure ethanol, about 8 grams of alcohol. A standard drink is defined differently in different countries, commonly around 10 g or 14 g. This calculator shows both 10 g and 14 g standard drink equivalents so you can compare with different guidelines.
The BAC estimates are approximate and based on population-average formulas. Real BAC can be higher or lower depending on factors such as genetics, health, food intake, medications and speed of drinking. Never rely on this or any online calculator when deciding whether you are safe or legal to drive or work.
Volume tells you how much liquid you drank, while ABV tells you how strong it is. Two drinks of the same size can have very different alcohol content if their ABV values differ. The units formula multiplies both volume and ABV to estimate the amount of pure alcohol.
You can always choose a generic unit such as milliliters, liters or fluid ounces and enter the exact volume printed on the label. The presets are provided for convenience but are not required to get an accurate calculation if you know the volume and ABV.
No. The calculator can help you understand quantities in terms of units and standard drinks, but it does not give medical advice or prescribe safe limits. Low-risk guidelines vary between countries, and personal health factors matter. Always follow local health authority guidance and talk to a health professional if you have concerns about alcohol use.