Lawyer's Rough Calculation of BAC

Simple Version

Click here for multiple drink version

Beer Wine Shot
Fluid Ounces 12, 16, 20 4, 6, 8, 10 1.0, 1.25, 1.5
Alcohol Content .04, .045, .05, .055, .06 .10 to .12 .40
 

 

Blood Alcohol Concentration is not the same as concentration of alcohol in the whole body. Not all of the body holds alcohol. Alcohol is not distributed uniformly throughout the body. The parts of the body that aren't blood, organs, and muscles don't hold much alcohol. Fat and bone don't absorb much. This means that you can't just divide alcohol by weight to get a concentration. You have to apply the Widmark r factor to adjust. For males the Widmark r factor is between 0.50 and 0.90 with an average of 0.70. For females the Widmark r factor is 0.45 to 0.63 with an average of 0.60. Try entering different values to obtain a range of possible results.

Different people eliminate or metabolize alcohol at different rates. Inexperienced drinkers metabolize their alcohol at a lower rate. The only way you can tell how fast a person metabolizes alcohol is to have a toxicologist perform experiments using controlled consumption of alcohol and frequent breath tests. That costs about $1400 for a day of lab experiments. If you don't know the elimination rate use the Widmark factor of between 10 and 20 mg/100mL per hour with an average of 15. Try entering different values to obtain a range of possible results.

You'll get different results if drinking isn't spread out evenly over the whole time. The alcohol has to be dissolved and absorbed into the body and that takes time, faster if a person has no food in the stomach and slower if they've had a big meal. These numbers assume that the alcohol consumption is spread out. If a person drank a lot more or had a shot of high alcohol percentage liquor towards the end of the evening these numbers won't work. If they gulped down a drink just before they left, the blood alcohol concentration may rise after they leave the bar and get caught driving, and rise even more while they wait to blow into the breath machine. For these kinds of calculations you need the help of a toxicologist. 

If a person drank different kinds of beverages during different time periods, the toxicologist will have to perform separate calculations for each drinking period, add them together (thinking about absorption rates), consider elimination, and then work out the totals at different times, maybe every 5 minutes. The lawyer may be able to do rough calculations, but ultimately you'll need to retain a toxicologist. Courts won't accept these simple mathematical calculations. The lawyer will have to obtain the Crown's consent to using the toxicologist's written report or affidavit in Court or if that doesn't work the toxicologist needs to be retained to come to Court for the day at a cost of about $1400.

This Calculator is designed to permit lawyers to explore a possible Carter defence. Don't use it to decide whether or not to drink and drive. It is dangerous to use these calculations to determine the ability to drive a vehicle or operate machinery after consuming alcohol. If you do so you assume full risk of legal prosecution, injury, illness, or death to yourself and others.

Conversion hyperlinks:

mLs  to Ounces and other volume

Widmark "r" Values 

Males

Wt lbs 99 110 121 132 143 154 165 176 187 198 209 220 231 242 253    
Wt kg 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115    
  0.78 0.75 0.72 0.69 0.67                     150 4'11"
  0.79 0.77 0.74 0.71 0.69 0.66                   155 5'1"
  0.80 0.78 0.76 0.73 0.71 0.69 0.66                 160 5'3"
  0.82 0.80 0.77 0.75 0.73 0.71 0.68 0.66               165 5'5"
  0.83 0.81 0.79 0.77 0.75 0.72 0.70 0.68 0.66             170 5'7"
    0.82 0.80 0.78 0.76 0.74 0.72 0.70 0.68 0.66           175 5'9"
    0.83 0.81 0.79 0.77 0.76 0.74 0.72 0.70 0.68 0.66         180 5'11"
      0.82 0.81 0.79 0.77 0.75 0.73 0.72 0.70 0.68 0.66       185 6'1"
      0.83 0.82 0.80 0.78 0.77 0.75 0.73 0.72 0.70 0.68 0.67     190 6'3"
        0.83 0.81 0.79 0.78 0.76 0.75 0.73 0.71 0.70 0.68 0.67   195 6'5"
        0.84 0.82 0.81 0.79 0.78 0.76 0.74 0.73 0.71 0.70 0.68 0.67 200 6'7"
          0.83 0.82 0.80 0.79 0.77 0.76 0.74 0.73 0.71 0.70 0.69 205 6'9"
                                Ht cm Ht ft,in

Females

Wt lbs 99 110 121 132 143 154 165 176 187 198 209 220 231 242 253    
Wt kg 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115    
  0.69 0.66 0.63 0.61 0.58                     150 4'11"
  0.70 0.68 0.65 0.63 0.60 0.57                   155 5'1"
  0.72 0.69 0.67 0.65 0.62 0.60 0.57                 160 5'3"
  0.73 0.71 0.69 0.66 0.64 0.62 0.59 0.57               165 5'5"
  0.74 0.72 0.70 0.68 0.66 0.64 0.61 0.59 0.57             170 5'7"
    0.73 0.71 0.69 0.67 0.65 0.63 0.61 0.59 0.57           175 5'9"
    0.74 0.73 0.71 0.69 0.67 0.65 0.63 0.61 0.59 0.57         180 5'11"
      0.74 0.72 0.70 0.68 0.66 0.65 0.63 0.61 0.59 0.57       185 6'1"
      0.75 0.73 0.71 0.70 0.68 0.66 0.64 0.63 0.61 0.59 0.58     190 6'3"
        0.74 0.72 0.71 0.69 0.68 0.66 0.64 0.63 0.61 0.59 0.58   195 6'5"
        0.75 0.73 0.72 0.70 0.69 0.67 0.66 0.64 0.63 0.61 0.60 0.58 200 6'7"
          0.74 0.73 0.71 0.70 0.69 0.67 0.66 0.64 0.63 0.61 0.60 205 6'9"
                                Ht cm Ht ft,in

 

Widmark r factor
table above
  Males (0.60 obese)(0.70 avg.)
Females(0.50 obese)(0.60 avg.)
Volume Consumed Alcohol Content (decimal e.g. .05)
Weight (Lbs)   Hours Consuming Drink                
Widmark factor 10 to 20 (avg. 15) mg/100mL per hour
  Total Metabolized Final
Min. Elim.10
Widmark
Max. Elim.20
BAC Analysis

 

 
 

 

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Stephen R. Biss, Barrister & Solicitor

470 Hensall Circle, Suite 303
Mississauga, Ontario
L5A 3V4

905-273-3322  or 1-877-273-3322

 


Advertisement. Any legal opinions expressed at this site relate to the Province of Ontario, Canada only. If you reside or carry on business in any other jurisdiction please consult a lawyer, solicitor, or attorney in your own jurisdiction. WARNING: All information contained herein is provided for the purpose of providing basic information only and should not be construed as formal legal advice. The author disclaims any and all liability resulting from reliance upon such information. You are strongly encouraged to seek and retain professional legal advice before relying upon any of the information contained herein.