Title: Unit of alcohol
Content: Half an imperial pint (284 ml) of beer with 3.5% ABV contains almost exactly one unit; however, most beers are stronger. In pubs in the United Kingdom, beers generally range from 3.5 to 5.5% ABV, and continental lagers start at around 4% ABV. An imperial pint of such lager (e.g., 568 ml at 5.2%) contains almost 3 units of alcohol rather than the oft-quoted 2 units. ; Stronger beer (6–12%) may contain 2 units or more per half pint (imperial). ; A half-litre (500 ml) of standard lager or ale (5%) contains 2.5 units. ; One litre (1000 ml) of typical Oktoberfest beer (5.5–6%) contains 5.5–6 units of alcohol. ; A beer bottle is typically 333-355ml, approximately 1.7 units at 5%. 
Title: Alcohol by volume
Content:  One calculation for beer is:
Title: Recommended maximum intake of alcoholic beverages
Content:  while in countries that use 12g, those same servings are 1.0, 1.6, 0.7, and 0.9 drinks respectively. Studies have shown that most people find it difficult to understand and define exactly what a standard drink is, and consistently underestimate how much they drink. The amount of pure alcohol is stated in the table in both grams and millilitres. The number of standard drinks contained in 500ml of beer of 5% ABV (a typical large drink of beer, similar to a US pint of 473ml) is stated for comparison. The amount of alcohol in any drink is calculated by the formula:
Title: Unit of alcohol
Content:  It is sometimes misleadingly stated that there is one unit per half-pint of beer, or small glass of wine, or single measure of spirits. However, such statements do not take into account the various strengths and volumes supplied in practice. For example, the ABV of beer typically varies from 3.5% to 5.5%. A typical "medium" glass of wine with 175 ml at 12% ABV has 2.1 units. And spirits, although typically 35–40% ABV, have single measures of 25 ml or 35 ml (so 1 or 1.4 units) depending on location. The misleading nature of "one unit per half-pint of beer, or small glass of wine, or single measure of spirits" can lead to people underestimating their alcohol intake.
Title: Beer
Content:  Beer ranges from less than 3% alcohol by volume (abv) to around 14% abv, though this strength can be increased to around 20% by re-pitching with champagne yeast, and to 55% abv by the freeze-distilling process. The alcohol content of beer varies by local practice or beer style. The pale lagers that most consumers are familiar with fall in the range of 4–6%, with a typical abv of 5%. The customary strength of British ales is quite low, with many session beers being around 4% abv. In Belgium, some beers, such as table beer are of such low alcohol content (1%–4%) that they are served instead of soft drinks in some 
Title: Alcoholic drink
Content: Wine and beer contain a similar range of ethanol quantity for servings of 5 USoz and 12 USoz, respectively, but these beverages also contain non-ethanol food energy. A 150 ml serving of wine contains 100 to 130 Calories. ; A 350 ml serving of beer contains 95 to 200 Calories. For example, in 12 USoz of 5% ABV beer, along with approximately 18 ml of alcohol (96 kcal), there are usually 10–15 g of carbohydrates (about 40 - 60 kcal). In addition to alcohol, many alcoholic drinks contain carbohydrates. Ignoring the non-alcohol contribution of those beverages, the average energy contributions are 48 and 108 cal/day, respectively. Excessive daily calorie intake may contribute to an increase in body weight and "beer belly". 
Title: Gravity (alcoholic beverage)
Content:  Knowing the amount of extract in 100 g of wort before fermentation and the number of grams of extract in 100 g of beer at its completion, the amount alcohol (in grams) formed during the fermentation can be determined. The formula follows, attributed to Balling  With typical values of 1.050 and 1.010 for, respectively, OG and FG this simplified formula gives an ABV of 5.31% as opposed to 5.23% for the more accurate formula. Formulas for alcohol similar to this last simple one abound in the brewing literature and are very popular among home brewers. Formulas such as this one make it possible to mark hydrometers with "potential alcohol" scales based on the assumption that the FG will be close to 1 which is more likely to be the case in wine making than in brewing and it is to vintners that these are usually sold.
Title: Unit of alcohol
Content:  UK guidance. One unit of alcohol (UK) is defined as 10 millilitres (8 grams) of pure alcohol. Typical drinks (i.e., typical quantities or servings of common alcoholic drinks) may contain 1–3 units of alcohol. Containers of alcoholic drinks sold directly to UK consumers are normally labelled to indicate the number of units of alcohol in a typical serving (optional) and in the full container (can or bottle), as well as information about responsible drinking. As an approximate guideline, a typical healthy adult can metabolise (break down) about one unit of alcohol per hour, although this may vary depending on sex, age, weight, health and many other factors.
Title: Recommended maximum intake of alcoholic beverages
Content:  corresponds to a typical 12 fl. oz. bottle of 5% Alcohol by Volume (ABV) beer, 5 fl. oz. of 12% ABV wine, or a 1.5 fl. oz. shot of 40% ABV liquor. Due to the different size of the US and Canadian ounce however, the actual amount of alcohol is slightly different. In Europe the most common standard drink size is 10g of pure alcohol, making a typical 330ml bottle of 4.8% ABV beer correspond to 1.2 drinks or a 500ml bottle 1.9 drinks; 100ml of 11% wine is 0.9 drinks, and a 40ml shot of 33% spirits equal 1.0 
Title: Unit of alcohol
Content:  The number of UK units of alcohol in a drink can be determined by multiplying the volume of the drink (in millilitres) by its percentage ABV, and dividing by 1000. For example, one imperial pint (568 ml) of beer at 4% alcohol by volume (ABV) contains:  Both pieces of input data are usually mentioned in this form on the bottle, so is easy to retrieve.

Question: how many grams of alcohol in one beer?
Answer: 14.
about 14 grams of alcohol.
14 grams.