To work out the number of units of alcohol, multiply the volume of the drink by the strength and divide by 1000. Wine will more often than not be 12%, and so one 750ml bottle will have 9 units. DoH reckons that "safe" drinking for men is 21 units a week spread over the week, and 4 units a day will not accrue significant health risk (and 14 is the figure for women, 3 units a day for women will not accrue significant health risks). Men drinking 50+ units per week and women drinking 35+ units per week are drinking at a harmful level for DoH purposes. Thus a man drinking 4.5 units 7 days a week drinks 32.5 units and is an "increasing risk" drinker but not drinking at a "harmful level"