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Calculating Your BAC

Blood Alcohol Content (BAC) Calculation

Estimate the percent of alcohol in the blood by number of drinks in relation to body weight. This percent can be estimated by:

  1. Count your drinks (1 drink equals 1 ounce of 100-proof liquor, one five ounce glass of table wine or one 12-ounce bottle of regular beer).
  2. Use the chart below and find the number of "drinks" in the top row and the "body weight" in the left column. Where the correct row and column meet, find the percent of blood alcohol listed.
  3. Subtract from this number the percent of alcohol "burned up" during the time elapsed since your first drink. This figure is .015% per hour. (Example: 180 lb. man - 8 drinks in 4 hours / .167% minus (.015x4) = .107 %
  1 2 3 4 5 6 7 8 9 10 11 12
100 lb. .038 .075 .113 .150 .188 .225 .263 .300 .338 .375 .413 .450
110 lb. .034 .066 .103 .137 .172 .207 .241 .275 .309 .344 .379 .412
120 lb. .031 .063 .094 .125 .156 .188 .219 .250 .281 .313 .344 .375
130 lb. .029 .058 .087 .116 .145 .174 .203 .232 .261 .290 .320 .348
140 lb. .027 .054 .080 .107 .134 .161 .188 .214 .241 .268 .295 .321
150 lb. .025 .050 .075 .100 .125 .151 .176 .201 .226 .251 .276 .301
160 lb. .023 .047 .070 .094 .117 .141 .164 .118 .211 .234 .258 .281
170 lb. .022 .045 .066 .088 .110 .132 .155 .178 .200 .221 .244 .265
180 lb. .021 .042 .063 .083 .104 .125 .146 .167 .188 .208 .229 .250
190 lb. .020 .040 .059 .079 .099 .119 .138 .158 .179 .198 .217 .237
200 lb. .019 .038 .056 .075 .094 .113 .131 .150 .169 .188 .206 .225
210 lb. .018 .036 .053 .071 .090 .107 .125 .143 .161 .179 .197 .215
220 lb. .017 .034 .051 .068 .085 .102 .119 .136 .153 .170 .188 .205
230 lb. .016 .032 .049 .065 .081 .098 .115 .130 .147 .163 .180 .196
240 lb. .016 .031 .047 .063 .078 .094 .109 .125 .141 .156 .172 .188

(Created from NHTSA chart, with modifications)

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