promille calculator

What is a promille calculator?

A promille calculator estimates your blood alcohol concentration (BAC) and expresses it in promille (‰), which means parts per thousand. In many countries, legal limits for driving are communicated in promille, making this format practical and familiar.

For example, a BAC of 0.5‰ means you have 0.5 grams of alcohol per liter of blood. Even low levels can affect reaction time, judgment, and coordination.

How this calculator works

1) Alcohol amount is converted into grams

The calculator converts each drink to pure alcohol grams using: grams = volume (ml) × ABV × 0.789, where 0.789 g/ml is ethanol density.

2) Widmark-based distribution estimate

Alcohol distributes differently depending on body composition. The calculator uses a common Widmark factor (r):

• Male: 0.68
• Female: 0.55
• Other/neutral estimate: 0.60

Initial BAC estimate: initial ‰ = alcohol grams ÷ (weight in kg × r)

3) Time-based reduction

Your body gradually eliminates alcohol. A typical average is around 0.15‰ per hour. The calculator subtracts this from the initial estimate based on the hours you entered.

Example

Suppose someone weighing 80 kg drinks 500 ml of beer at 5% ABV and 150 ml of wine at 12% ABV over two hours. The calculator estimates total grams of alcohol, computes initial promille, then subtracts approximately 0.30‰ for metabolism. The result is an approximation of current BAC.

Promille ranges and typical effects

• 0.00–0.19‰: Minimal noticeable effects in many people.
• 0.20–0.49‰: Mild impairment, reduced attention and divided-task performance.
• 0.50–0.79‰: Clear impairment in reaction time, tracking, and decision quality.
• 0.80–1.49‰: Significant motor and cognitive impairment.
• 1.50–2.99‰: Severe intoxication risk.
• 3.00‰ and above: Medical emergency risk increases substantially.

Why your real BAC can differ

Any BAC calculator is a model, not a lab test. Your true value can differ due to:

• Food in the stomach and meal timing
• Hydration level and fatigue
• Medication interactions
• Drinking speed (rapid intake spikes BAC)
• Hormonal and metabolic differences
• Health conditions and liver function

Legal and safety reminder

Laws vary by country and region. Some places use zero-tolerance limits for new drivers, commercial drivers, or specific age groups. Even if you are under a legal threshold, you may still be impaired.

The safest rule is simple: if you drank, do not drive. Use public transit, a taxi, rideshare, or a sober driver.

FAQ

Is this calculator accurate enough for legal decisions?

No. It is an educational estimate. Only certified testing methods are suitable for legal or medical purposes.

How long until I reach zero?

The calculator gives an estimated time based on 0.15‰ elimination per hour. Real rates vary, so treat it as a rough guide.

Can coffee or a cold shower lower promille faster?

No. They may make you feel more alert, but they do not significantly speed up alcohol elimination. Time is the primary factor.

Bottom line

A promille calculator is useful for awareness and risk reduction. Use it to make safer decisions early— and always choose caution over convenience when alcohol is involved.