Water Intake Calculator
Work out how much water you actually need each day. Enter your weight, how active you are, your climate, and whether you are pregnant or breastfeeding, and we will give you a target in litres and glasses.
Forget the one-size-fits-all eight glasses rule. How much water you need depends on your body size, how much you sweat, and the weather where you live. This calculator scales a baseline to your weight, then adds sensible top-ups for exercise, hot and humid climates, and the extra demands of pregnancy or breastfeeding.
It is built with Southeast Asia in mind, where heat and humidity quietly raise your fluid needs even on a lazy day in the office air-conditioning. Your result comes as litres, 250 ml glasses, and millilitres, so you can track it however suits you. Hydration also ties into your daily energy needs, so it pairs well with our guide to how many calories you need per day and the TDEE calculator.
Enter Your Details
💧 Your Daily Water Target
⚚️ Medical disclaimer: This calculator gives general estimates for educational purposes only. It is not medical advice and is not a substitute for guidance from a qualified doctor or dietitian. Individual needs vary. If you are pregnant, have a health condition, or have any concerns about your fluid intake, please speak with a healthcare professional.
How to Use This Calculator
Enter your weight
Switch between kg and lbs with the toggle. Body weight is the main driver of your baseline fluid needs.
Set activity and climate
Exercise and hot, humid weather both increase how much you sweat, so both raise your daily target.
Flag pregnancy or breastfeeding
Both raise fluid needs. Breastfeeding in particular adds a noticeable amount, so we top up your target.
Does coffee or tea count?
This is probably the most common hydration question, and the short answer is yes. Coffee and tea have a mild diuretic effect, which is why people assume they dry you out, but the fluid they contain more than makes up for it. In normal amounts they add net water to your body.
The evidence is clear. A 2014 study by Sophie Killer and colleagues, published in the journal PLOS ONE, gave regular coffee drinkers either coffee or water and found no difference in hydration across a day. Moderate coffee, they concluded, hydrates about as well as water. The US National Academies of Sciences reached a similar view, noting that caffeinated drinks count toward your daily water and that roughly 20 percent of our water actually comes from food.
So your morning kopi, teh tarik, or afternoon tea all count toward your target. Plain water is still the smartest default because it has no sugar or calories, but you do not need to discount your other drinks. The main exception is heavily sweetened drinks, which hydrate but bring a lot of sugar along for the ride.
Sources: Killer SC, Blannin AK, Jeukendrup AE. "No Evidence of Dehydration with Moderate Daily Coffee Intake." PLOS ONE, 2014, journals.plos.org. National Academies of Sciences, Engineering, and Medicine, Dietary Reference Intakes for Water (2004), nap.nationalacademies.org.
Frequently Asked Questions
How much water should I drink per day?
A common starting point is about 33 ml of water per kg of body weight. For a 60 kg person that is roughly 2.0 litres, or 8 glasses of 250 ml. Active people and anyone in a hot, humid climate like Singapore or Malaysia need more, often an extra 500 ml to 1 litre a day. This calculator adjusts your target for weight, activity, climate, and pregnancy.
How many glasses of water is 2 litres?
Two litres is 8 glasses if each glass holds 250 ml. This is where the familiar "8 glasses a day" guideline comes from. Glass sizes vary, so if you use a 500 ml bottle, 2 litres is 4 bottles. The calculator shows your target in litres, glasses, and millilitres so you can track it whichever way is easiest.
Does coffee or tea count toward daily water intake?
Yes. Despite a mild diuretic effect, coffee and tea add net fluid to your body. A 2014 study by Killer and colleagues in PLOS ONE found moderate coffee intake was as hydrating as water. The US National Academies also note that caffeinated drinks count toward daily water. Plain water is still the best choice, but your tea and kopi count too.
Do I need more water in Singapore and Southeast Asia?
Yes. In hot and humid Southeast Asian weather you lose more water through sweat even when resting, and sweat evaporates less efficiently in high humidity. Add at least 500 ml to your baseline, and more on days you are outdoors or exercising. For sweaty sessions over an hour, replace electrolytes like sodium too, not just water.
How do I know if I am drinking enough water?
The easiest check is urine colour. Pale straw to almost clear means you are well hydrated, while dark yellow or amber means drink more. Other signs of dehydration include headache, tiredness, dry mouth, dizziness, and poor concentration. Thirst is actually a late signal, so do not wait until you feel thirsty to drink.