Half a bottle (375mL) of 12% wine is 45mL of alcohol, or 4.5 UK "units", or 2½ US standard drinks. 750 mL ÷ 2 * 0.12 = 45 mL = 4.5 "UK units" 45mL * 0.789g

Half a bottle (375mL) of 12% wine is 45mL of alcohol, or 4.5 UK "units", or 2½ US standard drinks. 750 mL ÷ 2 * 0.12 = 45 mL = 4.5 "UK units" 45mL * 0.789g/mL ÷ 14 = 2.54 "US standard drinks"