BMI Calculator
Calculate your Body Mass Index and healthy weight range.
Open Tool →Water Intake Calculator
Find out exactly how much water your body needs each day. Personalised by weight, activity level, and climate — in litres, cups, and ounces.
Climate
Daily Water Target
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litres / day
In Cups (250 ml)
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cups/day
In Fluid Ounces
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fl oz/day
Space it out — Drink a glass on waking, one before each meal, and one before bed to hit your target easily.
Count food too — Around 20% of your daily water intake comes from food, especially fruits and vegetables.
Adjust for heat — Add 150–300 ml for every 30 minutes of exercise in hot conditions.
Coffee counts — Moderate caffeine intake (up to 400 mg/day) does not cause net dehydration for regular drinkers.
Daily Water Intake Calculator — How Much Water Do You Really Need?
Adequate hydration is one of the most important factors in overall health, yet most people drink less water than their body needs. The commonly cited "eight glasses a day" rule is a rough guideline — your actual requirement depends on your body weight, how active you are, the climate you live in, and what you eat. This calculator provides a personalised estimate based on these key variables.
The Formula Behind the Calculation
The base recommendation used by this calculator is approximately 35 ml per kilogram of body weight, which aligns with guidance from the European Food Safety Authority (EFSA) and many sports nutrition bodies. This baseline is then multiplied by an activity factor ranging from 1.0 (sedentary) to 1.6 (athlete-level daily training). If you live in a hot or humid climate, an additional 500 ml is added to compensate for increased sweating and evaporative water loss.
Signs You Are Not Drinking Enough
Mild dehydration (just 1–2% of body weight as fluid loss) can impair cognitive function, cause headaches, reduce physical performance, and lead to feelings of fatigue. Key warning signs of inadequate hydration include dark yellow or amber urine, infrequent urination (fewer than 4 times per day), dry mouth, dizziness on standing, and difficulty concentrating. The most reliable free indicator of hydration status is urine colour: pale straw to light yellow indicates good hydration; dark yellow to amber suggests you need more fluids.
Does the Type of Water Matter?
Plain water is the most effective hydration source. Herbal teas, diluted fruit juice, and milk also contribute meaningfully to daily fluid intake. Contrary to popular belief, moderate coffee and tea consumption (up to 400 mg of caffeine daily) does not cause net dehydration in habitual drinkers, as the fluid in the beverage outweighs any mild diuretic effect. Sugary drinks, energy drinks, and alcohol are poor hydration sources and should not be relied upon to meet your daily water target.
Hydration During Exercise
During sustained physical activity, sports medicine guidelines recommend drinking approximately 150–250 ml of water every 15–20 minutes. For exercise lasting more than 60 minutes, an electrolyte drink or food with sodium can help replace what is lost in sweat and prevent hyponatraemia (low blood sodium from over-drinking plain water). Always drink before you feel thirsty — thirst is a late indicator of dehydration.