Water Intake Calculator
Find out how much water you should drink per day based on your weight, activity level, and climate.
Daily Water Intake
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In glasses (250ml)
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In oz
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Includes all fluids. Needs vary by health status, medications, and pregnancy. Consult a doctor for personalised advice.
What is Water Intake Calculator?
The Water Intake Calculator estimates how much water you should drink per day based on your body weight, age, activity level, and climate. It provides your daily target in litres, standard glasses (250 ml), and fluid ounces so you can track intake in whatever unit you prefer.
How to use
- 1 Enter your body weight in kilograms.
- 2 Enter your age — the calculator slightly reduces the estimate for adults over 55.
- 3 Select your activity level from Low, Moderate, High, or Athlete.
- 4 Choose your climate: Temperate, Hot/Humid, or Very Hot.
- 5 Review your recommended daily water intake in litres, glasses, and ounces.
Formula
Example calculation
A 70 kg adult with high activity in a hot climate: base = 70 x 0.035 = 2.45 L, plus 0.7 L for activity and 0.3 L for heat = 3.45 L per day, or about 14 glasses.
Frequently asked questions
Does the 8 glasses a day rule have scientific backing?
The popular advice to drink 8 glasses (about 2 litres) a day is a rough guideline with limited direct scientific support. Actual needs vary significantly by body size, activity, climate, and individual metabolism. This calculator gives a personalised estimate.
Does coffee or tea count toward daily water intake?
Yes. Despite mild diuretic effects, caffeinated beverages like coffee and tea still contribute net fluid to the body. Water from food — particularly fruits and vegetables — also counts. This calculator covers all fluids.
How do I know if I am drinking enough water?
The simplest indicator is urine colour. Pale yellow means you are well hydrated; dark yellow or amber suggests you need more fluids. Thirst is also a reliable signal in healthy adults, though it lags slightly behind actual need.
Should I drink more water when exercising?
Yes. Exercise increases fluid loss through sweat. Add roughly 0.5-1 L per hour of moderate exercise. For intense or prolonged exercise in heat, consider electrolyte drinks in addition to plain water.
Can I drink too much water?
Yes — a condition called hyponatremia (water intoxication) can occur when excessive water intake dilutes sodium in the blood. It is rare in everyday life but can occur during extreme endurance events. Follow your thirst and stay within reasonable intake levels.