Water Intake Calculator: How Much Water Should You Drink?
Estimate how much water you need each day based on your body weight, exercise and climate, shown in litres, ounces, cups and bottles.
How much water should you drink a day?
A common starting point is about 30–35 ml of water per kg of body weight (roughly half an ounce per pound), plus extra for exercise and hot weather. For a 70 kg (155 lb) adult that’s around 2.3 litres from drinks.
The US National Academies set an “adequate intake” of about 3.7 litres a day for men and 2.7 litres for women, but that includes water from food, which provides roughly a fifth of the total.
What increases your water needs?
Exercise
Add about 350–500 ml for every 30 minutes of sweaty exercise.
Heat
Hot or humid weather can add half a litre or more a day.
Pregnancy
Needs rise a little in pregnancy and more while breastfeeding.
High protein
Higher-protein diets may slightly increase fluid needs.
Are you drinking enough?
Well hydrated
- Pale yellow urine
- Rarely feeling thirsty
- Steady energy through the day
Signs you need more
- Dark yellow urine
- Headaches, tiredness, dizziness
- Dry mouth or lips
Does drinking water help weight loss?
Water has no calories and can help you feel full, especially if you swap sugary drinks for it. Drinking a glass before meals may help some people eat a little less. But water itself doesn’t burn meaningful fat; a calorie deficit does.
Replacing one sugary drink a day can save 100–200 calories.
Water helps manage hunger on an intermittent fasting schedule.
Pair good hydration with a target from our calorie deficit calculator.
Water intake FAQs
Is 8 glasses of water a day enough?
Eight 8-oz glasses (about 2 litres) is a reasonable minimum for many adults, but larger and more active people usually need more.
Do coffee and tea count towards water intake?
Yes. Despite their mild diuretic effect, coffee and tea still contribute to your daily fluid intake.
How much water should I drink to lose weight?
The same as for health: around 30–35 ml per kg plus exercise. Drinking more than that won’t speed up fat loss.
Can you drink too much water?
Yes, though it’s rare. Drinking several litres very quickly can cause low blood sodium. Spread intake through the day.