Drink Driving Limit - Approximately....? - Hawesy1982
Hi everyone,

I post this as a result of a conversation i had in my local last night, that caused a fair bit of confusion, and which really would be helpful to know.

Although i personally don't drink at all if i'm going to be driving, many of my friends do, and although i know the legal limit is 80?mg/l? of alcohol in your bloodstream, and that this can vary depending on size/weight, APPROXIMATELY how much is this in standard 4-5% pints of lager???

For the life of me i can't find a conversion between mg/l and alcohol units anywhere, or i could do the calculating myself. It would just be nice to know whether or not my mates claims that "2 1/2 pints of Stella's fine" is really likely to be true, or if they'll quite possibly/definitely be over the limit.

On another note, i managed to calculate that last friday morning, after a big thursday night out and 3 hours sleep, i was over the limit until 3pm the next afternoon. Is this right? And if so was i running a serious risk in driving to work at 8am that morning, both legally and physically, as i felt 100% sober.

Any clarification would be good, especially from the legal people that i know give a lot of welcome advice here.


Drink Driving Limit - Approximately....? - smokie
Good question, but I don't think there is a "right" answer.

My rule of thumb used to be two pints max over an evening and having eaten. Whether that kept me legal I am never sure.

I am curious about the "next day" question and will be interested to hear replies. I heard that you burn it at the rate of 1 unit per hour, but how that relates to anything I don't know.
Drink Driving Limit - Approximately....? - Altea Ego
2 1/2 pints of Stella is probably going to see anyone knicked.

Ref your note about being legally over the limit till 3pm the next day then yes this is perfectly possible as many have found out when breathalysed the next morning/lunchtime
Drink Driving Limit - Approximately....? - GrumpyOldGit
Here are a few facts from searching the Internet.

See www.thinkroadsafety.gov.uk/drinkdrive/index.htm for government information.

How to work it out. (Number of units)

Multiply the volume/amount of drink in milliltres by percentage ABV (Alcohol By Volume), then divide by 1000.

For example with a 175ml glass of wine at 13% ABV
175 (amount) X 13 (%ABV) = 2,275

Divided by 1000 = 2.275 ie 2.3 units

Now let's take 1 pint of strong lager at 8% ABV
1 pint (568ml) X 8 = 4544

Divided by 1000 = 4.544 ie 4.5 units
The current legal limit for driving is 80mg of alcohol per 100ml of blood. In most European countries, the legal limit is 50mg. There is no failsafe guide to the amount of alcohol that a driver can safely consume - the amount and type of alcoholic drink, the weight, sex and metabolism of the driver all play a part.

Any amount of alcohol affects driving ability. A motorist's ability to judge speed and distance may be impaired, their reaction times may be slowed and their judgement of risk seriously affected.

An RAC survey found it was impossible to buy just one unit of wine in a pub. The myth of one small glass of wine being equivalent to one unit was based on 8 per cent strength wine, which is no longer widely available.
Nine people die every week on UK roads in drink related accidents - half of them innocent victims.

One unit is normally referred to as a glass of wine or a measure of spirit or a half-pint of beer.
The main problem with using this method of calculation is knowing exactly how much you have had to drink. The strength of beers varies tremendously, in pubs you get a measure of wine, whereas if you drink at home the glass size can vary.
This is a very unreliable way of calculating the level of alcohol within your body: Advice is very generalised and everyone's body reacts in different ways, making it impossible to tell how much alcohol is in your system without taking a breath test.
The only sure way is not to drink.

How long after drinking is it safe to drive?

Many people think that when they get in their car ?the morning after? they will be safe to legally drive, but will they?
Take a Saturday night's drinking:
·At midnight you may have 200 microgrammes per 100 millilitres of blood in your system. This is 2½ times the drink drive limit.

·At 7.30 a.m. there will still be 90 microgrammes per 100 millilitres in your system - you are still over the drink-drive limit.

·By lunchtime you will still have about 20 microgrammes in your system, not above the limit but still enough to adversely affect your driving. This is particularly important with society becoming more '24 hour' Because of shift rotas or flexi-time systems many people are at work before 7 a.m. And if they have been drinking on the previous evening they may still be over the limit when driving to work.

It is impossible to get alcohol out of your system quickly. Coffee and a shower will not speed the process up, it just takes time.

Personally I don't even have one drink if I'm driving. If I hurt someone after having a drink I couldn't live with it. That's the same thought that keeps me at 30mph in a 30 limit. Drink/driving and speeding are pure selfishness.
Drink Driving Limit - Approximately....? - Bromptonaut
Very difficult to answer this, as it varies with bodyweight, gender, rate of consumption absorption etc. Quick search from the relevant section of the DoH website revealed that neither the Portman Group nor Alcochol Concern would give a figure. Most people however grossly overestimate. It is very unlikley, unless you are a well fed bear, that two and a half pints of Stella (say 5 units/50ml pure alcohol) consumed in around an hour would leave you under the limit. I weigh approx 50kg and won't chance more than a half or a glass of wine, I am aware of having taken drink at those quantities. The 80mg in blood or 35 microgramme in breath limits is quite high, you are twice as likely to have an accident at 60mg in blood and as low as 20mg perception of speed and distance is affected.

One unit is equal to half a pint, single spirit measure glass of wine etc. It is also the rate per hour at which the body can eliminate alcohol. Fairly simple maths indicates just how far into the following morning a heavy session can put you over the limit.

The only real answer, however much of a wet blanket it sounds, is don’t drink at all if driving is a possibility.
Drink Driving Limit - Approximately....? - edisdead {P}
Also worth noting that Stella and other continental style lagers are significantly more potent than regular beers, upon which "half pint = 1 unit" is based. A pint of Stella contains three units of alcohol. Perhaps that's why it's known as "wife beater".
Drink Driving Limit - Approximately....? - Hawesy1982
Thanks for all your posts thus far, but there's still one glaring question:

We all know the limit is 80mg/100ml

We all know how many units in each drink


Okay, okay i know there's no hard and fast answer, but there must be some kind of generalisation that can be made, even if it's a cautious one, as then if you stay below that you are even more likely to be legal at least.

If it helps at all i'm a 20yr old Male, 180cm(5'11") and 70kg(11st)

Oh and doesn't exercise help alcohol leave your system quicker, due to upping your metabolic system? I always find if i've had a good dance before coming home of a night, i always feel relatively more sober than if i haven't
Drink Driving Limit - Approximately....? - edisdead {P}
"For the life of me i can't find a conversion between mg/l and alcohol units anywhere, or i could do the calculating myself"

Imagine what would happen if someone published research suggesting that the average male of average height and build can consume X pints of lager and be under the legal limit.

Not wishing to sound condescending - but I suspect the very reason this information is not available is to stop you calculating for yourself.
Drink Driving Limit - Approximately....? - Bromptonaut
That's the difficult bit 'cos units measure alcohol consumed and blood or breath alcohol the amount absorbed into the metabolism. Between the two are many variables. You might get away with a pint, even a pint and a half at your weight before hitting the limit. If you had an empty stomach and drank quickly you might be over. But even on the optimistic figure then you are at increased risk of accident. It won't loose you your licencse but it is contrary to advised ood practice and could count against you for liability in the event of an accident. Best to walk or taxi.
Drink Driving Limit - Approximately....? - Dwight Van Driver
Regrettably there is no magic table that you can refer to to check if you are under the limit. Its virtually all been said above why not.

I have know blokes have 3 -4 pints and come out just under and also some on 1 1/2 pints - 2 pints and be just over.

You want to be absolutely sure then do as it is advised " If you drink don't drive" otherwise when he comes at you with the tube
"You feel lucky punk?"

Drink Driving Limit - Approximately....? - bradgate
If it's any help to you, i have passed 2 breathalyser tests after consuming 2 pints of 4.5% abv bitter (eg Pedigree, Bass or London Pride) over the previous 1.5 - 2 hours, with nothing significant to eat. I was in my mid-to-late 20's at the time, 6'0 tall, and a somewhat lardy 15 stone.

After 2 pints my driving is definitely impaired, so these days i stick to 1 or 1.5 pints.

I am a big bloke and an experienced driver, but i would never consider driving after 2.5 pints of 5.2% abv Stella, and i would expect to fail a breath test on this quantity.

Better safe than sorry, surely?

Drink Driving Limit - Approximately....? - DieselBoy
Bradgate wrote "Better safe than sorry, surely?"

The only way to do this is to drink no alcohol. Zilch, zip, nuffing, nowt, diddly squat.

I had a "please blow into this tube" experience 7 years ago. Although I passed (just) and accepted 3 points for speeding like a big Christmas present, I felt ashamed that my driving was affected enough to be pulled over in the first place.

It ain't big, and it ain't clever!

Drink Driving Limit - Approximately....? - DougB
Having spent a lot of time drinking with Police & ex-Police (no connection) the opinion there is no more than 11/2 pints of beer. (in this case London Pride).

I know if I drink one pint, I drive in a very uninhibited manner (ie-like a lunatic). If I have more, I drive what I think is carefully but I know I'm kidding myself, so I just don't drink and drive.

Accidents can happen at any time, and if you have been drinking the consequenses are much worse.

Regards - DougB.
Drink Driving Limit - Approximately....? - Vin {P}
There really is NO WAY of telling.

A solicitor in a Northern town of whom I am aware tested himself when the new breathalyser came in (when the bags went). He borrowed one from the Police and had a session where he played rugby on a Sunday morning, drank a pint of milk, drank two pints of bitter, went home, had a Sunday dinner then went back to the pub for four more pints. He was a very big bloke, and he found that those six pints left him just under the limit. He tried it two weeks in a row and got the same results.

Then, you could take my wife (not a rugby player), give her two pints on an empty stomach and I'd bet my life she'd be over the limit.

So, with metabolism, stomach contents, size, amount of alcohol, dilution of alcohol, duration of drinking, etc all playing a part, the answer to your question is "no, there is no way of calculating".

Drink Driving Limit - Approximately....? - Robert Fleming
One pint ok.
Two, not so confident, but ok with a meal.
Three, forget it.

I'd wager the above is more reliable than a condom.
Drink Driving Limit - Approximately....? - cockle {P}
Dead right, absolutely no way of telling.

I, too, have a rugby playing friend, he ran an all day tournament at his club and drank steadily all day. After the tournament he got a lift home and then took the, stupid, chance of driving 100 yards down the road to the local takeaway, he pulled out a bit sharpish in front of a police car, without his lights on, and got pulled. Now, he reckoned he had drunk about 12 pints over the day but PASSED the breath test. Several weeks later he got pulled after having stopped for a couple of pints on the way home from work and promptly FAILED.

The only really safe way to know you are under the limit is to not drink, but I could never condone, as some do, a total zero alcohol level for drivers due to its impracticality. For instance, you could swallow some mouthwash when brushing your teeth in the morning and therefore be over a total zero limit.

I think the interesting thing to come out of this thread is that NO-ONE knows, or can possibly know, what the limit equates to in alcohol consumed. This puts someone who drinks anything in the situation of being unsure but that person has no way of being able to know for definite. Now, I know that the argument for not being able to have proper breath testers in pubs, etc. is so that people are not encouraged to drink up to the limit and still drive, but surely people ought to have the chance to avoid the penalty of an automatic ban and act sensibly and take a cab if near the limit.
I would draw the analogy that it would be like having an automatic ban if you are caught speeding, BUT, NO car is allowed to be fitted with a speedometer except for the police car which may be behind you.

Drink driving is one of very few offences that, if you are a little silly, you can commit without intent. Personally, I never take the risk as virtually none of the people that I know that have been convicted really thought that they were in any danger of being 'over the top'. The very knowledge of what they have gone through with a ban and consequent insurance premiums should be enough to keep anyone sober.

Drink Driving Limit - Approximately....? - DavidHM
The problem with nreath test machines in pubs is not so much that people on the borderline would be encouraged to drive; I reckon that would be outweighed by people over the limit being sobered up, so to speak, by seeing the reading, and deciding to leave the car behind.

However, if you've just downed your pint before you hit the road, some of that alcohol is still in your stomach, not your blood, and therefore the reading only applies at the moment you take it and not 20 minutes later when you crash into a parked car, stumble out and say "Not my fault offisher, I mushta had too mush to drink."

FWIW I reckon 1 pint okay, unless you're small and it's strong; 1.5 borderline, 2 if you're big, it's weak and you're lucky but in no way worth risking it. I personally consider one small glass of wine my drinking limit, and then only on really special occasions - about once a year maybe.

Of course there must have been times when I've been over the limit the morning after that, with hindsight, I really don't want to think about.
Drink Driving Limit - Approximately....? - cockle {P}
The problem with nreath test machines in pubs is not so
much that people on the borderline would be encouraged to drive;
I reckon that would be outweighed by people over the limit
being sobered up, so to speak, by seeing the reading, and
deciding to leave the car behind.
However, if you've just downed your pint before you hit the
road, some of that alcohol is still in your stomach, not
your blood, and therefore the reading only applies at the moment
you take it and not 20 minutes later when you crash
into a parked car, stumble out and say "Not my fault
offisher, I mushta had too mush to drink."

David, good point in para 2, but might it not be worth a trial somewhere just to see if the hardcore of drink drivers that the police keep on about could be shamed out of their cars? After all, I reckon the odds on the guy in para 2 having driven anyway would probably be pretty high but if it stopped one fatality it would be worth a go.

Drink Driving Limit - Approximately....? - Fullchat
Whilst your question is a good one there is no easy answer as you may have alredy gathered.

All I will say is this I have had the odious task of dealing with drink drivers and have found that there are so many factors that can effect the reading that there is no fullproof method of ascertaining fitness to drive. What I have found on several occasions, not withstanding imnpairment through other substances, is that sometimes despite demeanour people have come back under the limit when in my opinion those people had given me the impression that they were not fit to drive and I would stanby that opinion even after testing.
The main reading that is now used is 35 microgrammes of alcohol in 100 millilitres of breath. However no action will be taken for readings between 35 an 39, 40 is the magic figure which should relate to the reading of 80mg for blood.

Drink Driving Limit - Approximately....? - HisHonour {P}
There is really a very simple conversion. 1 unit of alcohol = do not drive. If you drink without driving or drive without drinking they can't touch you for it!

Before you all damn me for beng an unrealistic old fogey, just think for a minute and ask yourself if not drinking if you are driving isn't a sensible policy?

Most of us have done it - in my case, once, in my early twenties. Didn't gey stopped, didn't have an accident but when I got home I realised I had absolutely no business being behind the wheel and vowed never to do it again. Never have.
Drink Driving Limit - Approximately....? - SR
Have often wondered why it is that we have an offence (drink driving) that no-one can be absolutely sure whether or not they are guilty of until after they are caught.

I support the idea of a very low (near-zero) limit, and the only safe way to drive is not to drink, but how long do you have to wait after drinking before getting behind the wheel?

Would it be unreasonable for the police to offer a facility whereby a driver could wander into his local nick and ask to be voluntarily breathalysed (on reasonably accurate equipment) to make sure they're in the clear before driving?
Drink Driving Limit - Approximately....? - Hawesy1982
Thanks for all the replies thus far guys/girls, glad to see a seem to have sparked of a sensible debate here!

Just in case anyone was thinking otherwise, i rarely drink and drive myself, and if i do its only ever 1 pint at the very start of a night out, usually 3-5 hours before driving again.

I was just hoping for a general concensus on what would put you over, for my mates sakes they could do without a drink-drive conviction at the age of 20!

And it sounds as if the general idea is that the one pint rule shouldnt really be crossed if you want to be fairly sure of staying legal.

I must say that i like the idea of breathalysers in pubs tho, very simple to set up but could quite potentially save lives, eg. my mates checking after their 2 1/2 pints and seeing they are over, so not driving.

I'm sure they'd still consider themselves perfectly fit to drive, but the threat of a ban/fine etc from being randomly pulled at 11.20 just because they drive a boy-racer car, and subsequently getting done for drink-driving would surely be enough to make them drop to just the one pint at least.
Drink Driving Limit - Approximately....? - JamesH
I must say that i like the idea of breathalysers in
pubs tho, very simple to set up but could quite potentially
save lives, eg. my mates checking after their 2 1/2 pints
and seeing they are over, so not driving.

My thought on these devices is that they may help to save licences but not that many lives. If you feel the need to check then you could well be borderline and will be affected by the alcohol.

Suppose that 2.5 pints was the threshold for a particular person. Particularly amongst the young like myself, drinking a half has little 'credibility' so finishing off the last pint would take that person over.

One of the worst drinking times for me is lunchtime as alcohol seems to affect me more then than in the evening. I won't use the car for several hours after a lunchtime drink.

Drink Driving Limit - Approximately....? - neil
And they could have a booth where you could confess to any crimes you might think you've committed, while you're there... oh hang on this one's already appeared in Viz...

Value my car