How do you calculate BAC, confused?

[Routemaster]

A few questions after reading about blood alcohol content BAC on http://www.drinkdriving.org/drink_driving_information_bloodalcoholcontentcalculator.php.

Sorry to be a bit mathematical lol

1) If an average adult has 5 litres of blood or 5000 ml and the maximum legal limit is 0.08% of alcohol then how's this?

You drink a 750 ml bottle of 13% proof red wine which means you will have consumed 97.5 ml of pure alcohol (0.13 x 750= 97.5)

then in an average adult 97.5ml / 5000ml = 0.0195 x 100 = 1.95%

so surely that can't be right that after drinking a full bottle of wine your BAC is only around 2%?


2) the BAC calculator page says that it takes an average person 1 hour to eliminate 15 ml of alcohol from the body. So going by our bottle of red wine which contains 97.5 ml of pure alcohol it would take 97.5 ml / 15 ml = 6.5 hrs

Surely it would take far longer than 6.5 hrs to eliminate the alcohol from a bottle of 13% wine? More like 10 hrs at least 12 to be safe.

I know that peak BAC is reached 30 mins after last drink is finished so you'd add half an hour so it would be 7 hrs in this case after your last sip of wine.

Its also well known that it takes 1 hr for the average adult to eliminate 1 UK unit of alcohol. If our bottle of wine is 10 units then it would be 10 hrs.

are my calculations wrong?

 

[Forum Moderator]

A few questions after reading about blood alcohol content BAC on http://www.drinkdriving.org/drink_driving_information_bloodalcoholcontentcalculator.php.

Sorry to be a bit mathematical lol

1) If an average adult has 5 litres of blood or 5000 ml and the maximum legal limit is 0.08% of alcohol then how's this?

You drink a 750 ml bottle of 13% proof red wine which means you will have consumed 97.5 ml of pure alcohol (0.13 x 750= 97.5)

then in an average adult 97.5ml / 5000ml = 0.0195 x 100 = 1.95%

so surely that can't be right that after drinking a full bottle of wine your BAC is only around 2%?


2) the BAC calculator page says that it takes an average person 1 hour to eliminate 15 ml of alcohol from the body. So going by our bottle of red wine which contains 97.5 ml of pure alcohol it would take 97.5 ml / 15 ml = 6.5 hrs

Surely it would take far longer than 6.5 hrs to eliminate the alcohol from a bottle of 13% wine? More like 10 hrs at least 12 to be safe.

I know that peak BAC is reached 30 mins after last drink is finished so you'd add half an hour so it would be 7 hrs in this case after your last sip of wine.

Its also well known that it takes 1 hr for the average adult to eliminate 1 UK unit of alcohol. If our bottle of wine is 10 units then it would be 10 hrs.

are my calculations wrong?

If you input the following information into the BAC calculator:

• SEX: Male
• WEIGHT: 80 kg
• DRINK: 750 ml of 13% wine

Then input different times ranging up to 10 hours, you will see that it does indeed take approximately 10 hours before the calculator produces a BAC result of 0.

The 15ml average elimination rate stated on said page should be changed to 10ml to correspond with the BAC calculator results and the one unit per hour elimination rate theory.

Not everybody is 'average' though and there are numerous factors that can influence a persons BAC at any given time.

The old adage is certainly true, "If in doubt, do not drive!".

 

[Routemaster]

If you input the following information into the BAC calculator:

• SEX: Male
• WEIGHT: 80 kg
• DRINK: 750 ml of 13% wine

Then input different times ranging up to 10 hours, you will see that it does indeed take approximately 10 hours before the calculator produces a BAC result of 0.

The 15ml average elimination rate stated on said page should be changed to 10ml to correspond with the BAC calculator results and the one unit per hour elimination rate theory.

Not everybody is 'average' though and there are numerous factors that can influence a persons BAC at any given time.

The old adage is certainly true, "If in doubt, do not drive!".

thanks that does make sense. I couldn't actually get the calculator to work on my Ipad.