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Fitness & Wellbeing

How much water
should you drink?

Your personalised daily hydration target — based on your weight, activity level, climate, and health status. Get your target in litres, glasses, and a drink-by-drink schedule.

Your Details
Weight
Unit
Activity Level
Climate
Additional Factors
🤰
Pregnant
+0.3 L/day
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Breastfeeding
+0.7 L/day
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High Altitude
+0.5 L/day
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Fever / Illness
+0.5 L/day
Wake-up time (for schedule)
Daily Water Target
2.4
litres per day · 2,400 ml
Recommended range: 2.1 – 2.7 L
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Glasses (250ml)
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Bottles (500ml)
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Fluid oz
What's included in your target
Suggested Drinking Schedule
Hydration Tips
🌅
Start with 500ml on waking — you lose ~500ml of water overnight through breathing and sweat. Drinking a large glass first thing jumpstarts your metabolism and is the single easiest hydration habit to build.
☕
Coffee and tea count (mostly) — caffeine has a mild diuretic effect but research shows caffeinated drinks still contribute net fluid. Count them at ~80% of their volume. Alcohol, however, is genuinely dehydrating and increases your needs.
🥗
Food provides ~20% of hydration — fruits and vegetables are 80–95% water. A diet rich in whole foods meaningfully reduces how much you need to drink. This calculator accounts for the remaining 80% that should come from beverages.
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Check your urine colour — pale straw yellow means well hydrated. Dark yellow or amber means drink more. Clear is slightly over-hydrated (not dangerous, just unnecessary). This is the simplest real-time hydration test available.
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Don't rely on thirst alone — by the time you feel thirsty, you are already mildly dehydrated (around 1–2% fluid deficit). Use the schedule above as a prompt, or set phone reminders at your drinking intervals.

How is the target calculated?

The base formula is 35ml per kg of bodyweight — a widely cited clinical guideline. This is then adjusted upward for activity (sweat loss), climate (heat-driven fluid loss), and health factors. The final number represents total daily fluid from beverages — about 80% of your total water needs.

Does coffee count as water?

Yes, with a caveat. Despite myths, research confirms that moderate caffeine intake doesn't cause net fluid loss in habituated drinkers. Caffeinated drinks count toward hydration at roughly 80% of their volume. Alcohol is the exception — it actively increases water excretion and should not be counted.

Why does activity increase needs so much?

You can lose 0.5–2 litres of sweat per hour of exercise depending on intensity and heat. Even moderate exercise in a cool environment produces significant fluid loss. Endurance athletes in hot weather can lose 3+ litres per hour — making hydration as important as fuelling for performance.

Pair with your macro targets

Water intake and nutrition are closely linked. Use the Macro Calculator to set your calorie and protein targets, and the Calorie Deficit Calculator if you're losing weight — higher protein diets and caloric deficits both increase hydration needs slightly.

Frequently Asked Questions
How much water should I drink per day? ▾
The most personalised answer is based on your bodyweight: roughly 35ml per kg. A 70kg person needs about 2.45L of fluid daily from drinks. General guidance (8 glasses/day, or 2L) is a rough average that doesn't account for bodyweight, activity, or climate. This calculator gives you a personalised target that does.
Can I drink too much water? ▾
Yes, but it's rare outside extreme endurance sports. Drinking far more water than your kidneys can process (more than ~1L per hour) can dilute sodium levels, causing hyponatremia — a serious condition. For ordinary healthy adults following this calculator's guidance, overhydration is not a meaningful concern. Sip steadily throughout the day rather than drinking large volumes at once.
Does the 8 glasses rule have any basis? ▾
It's a simplification. The "8×8" rule (eight 8oz glasses = ~1.9L) traces back to a 1945 US Food and Nutrition Board recommendation that was widely misquoted over decades. It has no strong scientific basis as a universal target. 2L/day is about right for a sedentary 60–65kg person in a temperate climate — but wildly off for larger, more active, or heat-exposed individuals.
Does water intake affect weight loss? ▾
Yes, in several ways. Drinking water before meals reduces calorie intake by promoting fullness. Cold water slightly raises metabolism (thermogenic effect). Adequate hydration is required for efficient fat metabolism. And dehydration is often misread as hunger, leading to unnecessary snacking. Use the Calorie Deficit Calculator alongside this tool for a complete weight loss approach.
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✅
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💧 Today's Intake Tracker
Tap a glass to log it. Goal pulled from your calculation above.
0 / 8 glasses 0%
Last 7 days
How to Use the Water Intake Calculator

Calculate your personalised daily water intake target based on weight, activity, and climate.

01
Enter your body weight
Use your current weight in kg or lbs. Heavier individuals have higher fluid requirements because they have more metabolically active tissue.
02
Set your activity level
Light activity (desk job, occasional walks) requires less water. Intense daily exercise requires significantly more — sweating is the main variable.
03
Select your climate
Hot or humid climates increase water loss through sweat even during rest. Add the climate modifier if relevant.
04
Review your daily target
The result is shown in litres, ml, and the equivalent number of standard glasses (250ml each). This is your total fluid intake — including water in food, tea, coffee, etc.
05
Track throughout the day
Use the 'I drank a glass' button to track progress toward your daily goal. The visual progress bar shows where you are.
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💡 Coffee and tea count toward hydration despite the mild diuretic effect — the fluid gained significantly outweighs the fluid lost. The 'coffee dehydrates you' myth is not well supported by the evidence.