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How Much Water Do You Need In a Day?

Every now and again, I’ll go to write a blog post that I assume will be somewhat straightforward until I start doing research and realize it just so isn’t. This is a perfect example of that situation. We’ve been told all our lives that eight glasses of water a day is sufficient, but the truth is this is far too simplistic. In reality, there are many factors that affect our water needs, such as our weight and activity level. By the end of today’s post you should be confident knowing how much water your body needs.

How to Calculate Your Body’s Water Needs

The calculation below was created by The University of Missouri based on recommendations by The American College of Sports Medicine and U.S. News and World Report. I like it because it’s personalized without being excessively complicated. Here it is: 

  1. Calculate your water needs for your weight. 

  • Your weight divided by 2 = oz. of water needed per day

    • Ex: 130 ÷ 2 = 65 oz.) 

  • That number x 29.5 = millilitres of water needed per day 

    • Ex: 65 oz. 29.5 = 1,917.5mL of water per day

2. Take your exercise into consideration. 

  • Final number from part 1 + (minutes of exercise ÷ 30 minutes x 354.8mL) = mL of water per day 

    • Ex: 1,917.5 + (30 minutes of exercise / 30 minutes x 354.8mL)

= 1,917.5 + (1 x 354.8mL)

=2,272.3mL of water needed per day 

3. Take caffeine intake into consideration. 

  • The result you get from part 1 and 2 is the amount of water you need if you don't drink any caffeinated beverages. As caffeine is a diuretic, you'll need to counteract the effects with additional water. The best rule of thumb is to drink two cups of water for every cup of coffee. 

4. Pregnant? You need more water.

  • Pregnant women should increase their fluid intake by 709 - 946 mL based on their weight.

To make things a little easier for you, I’ve created the following chart to help you figure out your daily water needs. If you exercise, you’ll have to use the calculation above to take that into consideration:

What Symptoms Result from Dehydration? 

Many of us prefer drinking coffee, tea, pop, or fruit juices instead of plain ol’ water. But even though these options contain water, their caffeine or sugar content can negatively affect the rate of absorption. As a result, many of us are dehydrated a lot of the time, which leads to a number of problems according to the British Nutrition Foundation and Nutrition Reviews, such as: 

  • Impaired cognitive function, specifically in terms of concentration, alertness, and even short-term memory

  • Dry skin 

  • Decreases in blood volume and increases in hypotension 

  • Mood disruptions

  • Reduced physical performance (i.e. in sports) 

  • Constipation 

  • Fatigue

  • Headaches

Anecdotally speaking, many people have also attributed clear, acne-free skin to increased water intake, suggesting that dehydration could somehow be connected to acne. 

It is worth noting how common the above symptoms are. Poor concentration, constipation, moodiness are symptoms that many people experience on a daily basis, but simply chugging back water could significantly help. 

What About Food? 

About 20% of our diet comes from food according to the British Nutrition Foundation, but of course this number will vary drastically depending on the foods we eat. While berries, melons, citrus fruits, apples, and leafy greens contain about 90 - 95% water, savoury snacks or candy contain only 1 - 10% water. 

It would also take a lot of extra work and math to figure out how many millilitres of water your food provides per day, so sticking to the table provided in this blog post is your best bet. 

The Bottom Line

The whole “eight-glasses-of-water-per-day” message is not only outdated, but inaccurate. Many of us need more water than that recommendation based on our weight, how much we exercise, and how much caffeine we drink. 

 If you struggle to drink the amount of water recommended for you in this blog post, try keeping bottles of water in plain sight as a visual reminder to drink up. Alternatively, I’ve heard of some people putting an elastic on their wrist to signify the number of bottles/cups of water they need to drink throughout the day—and removing one for every cup drank. Finally, try flavouring your water with mint leaves, fruit, lemon, lime, grapefruit, or whatever you prefer. 

Also, if you're someone who struggles to drink water YOU NEED THE "PLANT NANNY" APP IN YOUR LIFE. It's an app that involves feeding an adorable cartoon plant water every time you drink so it can grow—just like a tamagotchi from the 90s! Don't ask me why but apparently I care way more about if my plant is happy than if my own organs are.

You Tell Me!

What tips do you use to stay hydrated throughout the day? Share your advice in the comments below!  


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