Curse that thin red (or white) line

Does anyone actually notice the ''standard drinks'' information on wine labels? And if so, do they know how to make use of it?

On the back of my bottle of Penfolds Bin 389 Cabernet Shiraz 2010 is a little black wine glass with ''8.6 standard drinks'' printed beside it. Hands up those who know what it means and how to use it. Very few, I'd wager.

Just in time for Dry July, the new Jacob's Creek standard drinks phone app, called The Wine Line, has arrived. It's a natty idea, using your phone camera, and seems to have good intentions as far as gauging how many standard drinks are in your wineglass. However, it ignores the most important guidance needed by drinkers wanting to regulate their alcohol intake.

What is actually meant by a standard drink? And how can we use the information to regulate our alcohol intake? It doesn't attempt to answer the question of how many standard drinks a day or an hour are acceptable for general health or when driving a car. The last is the trickiest: few experts want to be quoted saying any level of drinking is compatible with driving.

There are some click-through links to other helpful websites, but the information could be presented more quickly and simply on the app itself.

Simply, the app - which is free from the App Store - claims to enable you to work out how many standard drinks (a standard drink is a 10-gram serve of alcohol) are in your glass. It works by taking a photograph of your glass of wine. You trace the outline of the wine in your glass on the screen, and tap in the percentage alcohol of that wine as stated on the label, then it calculates how many standard drinks are in the glass. The app also keeps a tally of the standard drinks you've had during a session - but you'll have to keep photographing each glass as it's poured - and don't allow anyone to top it up, of course.

The idea of using my less-than-delicate digit on a phone screen to draw the outline of wine in a glass seems a bit crude but, after a few attempts, it's surprising how accurate even a fumble-fingered bloke can be.

A standard drink is calculated as follows. It's the volume of liquid as expressed as litres (0.75 in that bottle of Penfolds) multiplied by the alcohol percentage as stated on the bottle (14.5 for this wine) multiplied by 0.789. So for the Penfolds, it's 8.6 standard drinks.

Imagine you're in a restaurant with your partner (in old-fashioned male-female configuration) and you're wondering how to gainfully use this new-found information. The National Health and Medical Research Council (NHMRC) recommends a limit of two standard drinks a day for both men and women, for good health. This used to be different: twice as much for men as women, based on their greater average body mass, but the NHMRC changed its message a few years ago. The present guidelines mean you can safely share about half a bottle of the Penfolds wine between you, 50/50. Save the other half for the next evening.

What about the common situation of wine by the glass? I've just poured myself what I think is an average glassful of the Bin 389 - it's actually 150 millilitres, which is a typical restaurant pour - and my phone has The Wine Line app loaded and ready. I shoot, draw the outline of the wine in the glass, enter 14.5 per cent alcohol, and I'm told I have 2.1 standard drinks.

This is a bad start. If The Wine Line calculation was correct, there would be 10.5 standard drinks in the bottle, not 8.6! Not at all accurate. And repeating the process, I got this result again and again. The glass was a wide-bowl Riedel shiraz glass. I transferred the same serve of wine to a different-shaped Riedel glass, and what do you know: I received a range of different readings: 1.2, 1.5, 1.6, 1.7, and 2.1 standard drinks. The correct answer should be 1.72. I could be entirely to blame, I suppose. I could just be very poor at drawing with my finger on a phone screen.

So, I came away not being a big believer in The Wine Line. It seems to be a good promotional tool for the company's own range of wines, though, which are there on the app.

It's worth noting that wines vary widely in their alcohol content. Anyone assuming all wines are similar could be in for trouble. A semillon with 11 per cent alcohol contains 6.5 standard drinks compared with our Penfolds red at 8.6; indeed, many delicate dry white wines are very low in alcohol. Note that a semillon or riesling with 10 per cent alcohol contains 50 per cent less alcohol than a big shiraz with 15 per cent. You can drink three glasses with the same effect as two of the shiraz.

A standard drink and you

One standard drink is 10 grams of alcohol, irrespective of the type of drink and container.

A useful rule of thumb: a 100-millilitre serve of an average wine of 13 per cent alcohol is one standard drink. Hence, a standard restaurant pour of 150 millilitres is 1½ standard drinks.

The National Health and Medical Research Council recommends a safe limit of two standard drinks a day for both sexes.

What about driving? The Centre for Automotive Safety Research (CASR) at the University of Adelaide says that to remain under the legal limit of 0.05 per cent blood alcohol concentration, women should consume no more than one standard drink in the first hour and one each hour following; for men, no more than two standard drinks in the first hour, and one each hour following. However, CASR (CASR) says wine drinkers should not drink and drive at all.

An international conference, WineHealth 2013, will be held in Sydney on July 18-20, at the Convention and Exhibition Centre, Darling Harbour. Experts from around the world will present the latest research on the relationship between wine consumption and health. Aspects will include cardiovascular, pharmacological, ageing, cognitive function, psychological, nutrition and lifestyle. See winehealth.com.au.

● More information: see drinkwise.org.au.

● The Australian Wine Research Institute website has a lot of information, including the wine and health information booklet. See awri.com.au.