I thought it is pretty simple:

One US unit = 17 ml of pure ethanol.
One UK unit = 10 ml of pure ethanol

These days, nearly all red wines have 13-14% alcohol by volume. Then each 750 ml bottle is 97.5-105 ml = 5.7-6.2 US units. So on average, a bottle of wine is approximately 6 US and 10 UK units.

Vast majority of beers are withing 5-6%. Since six pack is 2 L, it fits another definition of a single US drink as being a singe 0.33L bottle/can of beer well enough. A six pack is 6-7 US and 10-12 UK units.

Almost all hard liquor is 40%, so a typical 750 ml bottle is about 18 US and exactly 30 UK units.

Thanks a lot ortho!

I've never come across a definition of the UK unit calculation before, despite lots of time online (but then more fool me, I looked hardest of all on the government National 'Health' Service info sites )

It makes perfect sense the way you put it

In the UK, though, most people drink beer in pubs by the UK pint (568ml) or the half-pint. Most beers here are in the 4 to 5% range (ales are typically a little lighter, but can equally go much stronger). Cans for home 'administration' of this horrendous substance are usually 440ml or 500ml - alcoholics rarely bother to buy bottles of 330ml We have two types of lager (my former favourite tipple) - the 'regular' stuff, and the premium lagers. Regular lagers are usually in the 4%+ range, and the premiums are the high 4s+.

A pint of Stella (5%) is 3 UK units.

I think wines have slightly more units than you've calculated? I used to drink a white labelled as 12.5% alcohol and 10 units - so a 14% must be beyond that (but then maths is not my strong point, and in any case most drinks in the UK have the info on the bottle or can anyway).

the simplest way, in my opinion, to do these calculations, is to take a 'standard' quantity of your favourite tipple (or tipples if you have more than 1!!) - e.g. a bottle of wine, and do the calculation once.

UK units are far easier to do the calculations with. 1 UK unit is 10ml of pure alcohol.

If you have 1.5L bottle of win, then every 1% alcohol is 1.5 units, so you're probably looking at 18-21 units per bottle. Call it 20 if you want to keep the calculations simple. Now keep track of how many bottles or fractions of bottles you drink per day and multiply that by 20 and hey, presto - you have your units

I wouldn't obsess about being absolutely precise, it is more important to be consistent - after all the trend is the important thing and if and when you get to the stage of drinking 10 units or less per week and no more than 2 per sitting, it won't really matter if 'your unit' is 9ml, 10ml or 12ml of pure alcohol.