The amount of water you should actually consume every day? It's not 8 glasses.

Even if you’re not diligent about drinking water, you’ve probably heard that eight glasses is the target.

Everyone from glowy-faced supermodels to mums will tell you drinking this magical amount of water keeps your complexion clearer than an Alpine stream, wards off headaches and ensures all your organs are chugging along happily.

However, the amount of water we need to drink is not necessarily that straightforward.

“As a rough estimate, The Australian Nutrient Reference Values recommends about 2-2.5 litres,” explains Professor Tim Crowe from Deakin University’s School of Exercise and Nutrition Sciences.

This equates to about eight glasses a day, but as with almost anything health-related there’s no ‘one size fits all’ approach to water intake. A number of factors can influence how much an individual needs, including the climate they live in, body size, diet, and in particular, how physically active they are.

“For every hour you’re working out, you should be adding on an additional litre of water,” Sydney-based personal trainer Kirsty Welsh recommends.

The ‘eight glasses a day’ figure is believed to have originated from a 1945 statement from the US Food and Nutrition Board of the National Research Council. The Board members wrote: “A suitable allowance for adults is 2.5 litres daily in most instances. Most of this quantity is contained in prepared foods”.

Clearly the 2.5 litre figure has stuck in popular memory – but it seems the second half of that passage has been drowned out over time. For this reason, people might assume their daily fluid intake needs to come from water specifically, even though they’re being hydrated in other ways.

“[The daily intake] can be tea, it can be milk, it can be fruit juice and it can be coffee. It’s a bit of a myth that coffee dehydrates you – you get loads of water in your cup of coffee and you only lose a small amount from caffeine,” Professor Crowe says. Food can also contribute to your fluid intake, particularly fruits and vegetables.

Of course, it’s important to remember that water is a more nutritious source of fluid than some other beverages because it doesn’t contain sugar or additives. If you find water hard to drink, Kirsty Welsh recommends adding a lemongrass teabag, or some fruit and herbs to add flavour (her favourite combination is cucumber, mint and lemon wedges). Herbal tea is another healthy way to stay hydrated.

Although it’s great to be diligent about chugging H2O, it is also possible to overdo it; if you’re a regular, otherwise healthy person, four litres in a day is pushing the upper limit.

According to health experts in a recent Daily Mail report, excess sweating and disturbed sleep are some possible outcomes of consuming too much water. In more extreme cases something called ‘water intoxication‘ can occur, as over-hydrating disrupts the body’s normal balance of electrolytes.

“The symptoms that [water intoxication] presents – you actually feel a bit drunk to start with, it causes blurred vision, you can feel light-headed, you can have poor muscle coordination. And that can progress enough that your brain swells, the pressure builds up and that can be fatal,” Professor Crowe explains.

This is a rare occurrence, though, and one that’s not easy to achieve – you’d need to be drinking around four litres of water an hour without exercising to hit that make.

On the other hand, staying properly hydrated boasts myriad benefits for your health and wellbeing.

“If you think about the fact that we’re 80% water, it vouches for the fact that every single cell in our body requires water to function properly,” Kirsty Welsh explains.

Bustle writer Maxine Builder recently documented her week-long attempt to drink 91 ounces of water per day (about 2.7L) – the amount some health experts recommend for women

At the end of the experiment, Builder noted that she had become more conscious of her unhealthy habits, consumed less alcohol and soft drink and stopped snacking needlessly. The skin improvements she’d read so much about didn’t eventuate, but this is possibly because the trial period was only 7 days and Builder didn’t adjust anything else in her routine.

“The acne on my chin subsided a little, but it’s hard to know if that’s because of the increased intake of water or because I just waited it out long enough … The dark circles under my eyes that I hoped would be erased totally stayed put,” she writes.

Click through to see how you can make drinking water more enjoyable… 

Despite the Daily Mail‘s claims, Professor Crowe believes it’s better to slightly over-hydrate yourself than not drink enough water. He says that usually your body will let you know when you’ve overdone it – in other words, you’ll need to hit the toilet more than usual and you’ll start feeling incredibly full and bloated.

At this point, you might be wondering how to figure out your optimum water intake.

“There’s a scientific formula I’ve heard before for how much water you should be drinking,” Kirsty Welsh says. “If you times your body weight in kilos by .033, that is supposed to be the magic number in litres. So if you’re around 60-62 kilos, it’ll be about 2 litres.”

However, paying attention to your body and how you feel throughout the day is an equally effective approach (and on the upside, doesn’t involve maths…).

“When you’re not getting enough water, you’ll be tired, you’ll be lethargic, you’ll probably feel hungry or think you’re hungry – you’re reaching for energy but really you’re sluggish and lethargic because your body is searching for more water,” Kirsty says.

“I have a foolproof guide to determining whether you’re getting enough water – you can check it 5 or 6 times a day, every time you go to the toilet. If your wee’s really clear or pale yellow, you’re drinking enough. If it’s very dark you need to drink more. That’s all you really need to worry about,” Professor Crowe says.

How much water do you drink in an average day?

Want more? How about:

Can your plastic water bottle give you cancer?

Feeling thirsty? Read this.