How much water should I drink per day?

Use the formula: body weight (kg) × 35 ml. A 70 kg person needs about 2.45 litres daily. Adjust for exercise, hot climate, and altitude. Best indicator is urine color — aim for pale straw.

Does tea or coffee count towards water intake?

Yes. Despite caffeine's mild diuretic effect, the water content provides net positive hydration. However, water should still be your primary source.

Is it possible to drink too much water?

Yes. Overhydration (hyponatremia) can occur when blood sodium levels drop. If urine is consistently colorless, you may be drinking too much.

Should I drink more water in summer?

Absolutely. In temperatures above 35°C, increase intake by 500–1000 ml and include electrolyte-rich drinks if spending time outdoors.

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How Much Water Should You Drink Per Day? (By Weight & Activity)

Calculate your daily water intake based on body weight and activity level. Hydration guide with myths busted.

10 June 2025 6 min read

water intakehydrationhealthdaily waterwellness

The Simple Formula

The most reliable way to estimate daily water need is based on body weight:

Daily Water Intake (ml) = Body Weight (kg) × 35

A 70 kg person needs approximately 70 × 35 = 2,450 ml (about 2.5 litres) per day. This is your baseline for a sedentary lifestyle in moderate climate.

Adjustments are needed for activity level, climate, and health conditions.

Water Intake by Body Weight

Quick reference for daily water needs based on weight and activity:

Body Weight (kg)	Sedentary	Moderate Activity	Heavy Activity
40 kg	1.4 L	1.8 L	2.2 L
50 kg	1.75 L	2.2 L	2.7 L
60 kg	2.1 L	2.6 L	3.2 L
70 kg	2.45 L	3.1 L	3.7 L
80 kg	2.8 L	3.5 L	4.2 L
90 kg	3.15 L	3.9 L	4.7 L
100 kg	3.5 L	4.3 L	5.2 L

Climate and Activity Adjustments

Your baseline needs adjustment in several situations:

Hot climate (Indian summers): Add 500–1000 ml in temperatures above 35°C.
Exercise: Add 500 ml per 30 minutes of moderate exercise. Up to 1 litre per hour for intense exercise.
High altitude: Add 300–500 ml due to faster breathing.
Air-conditioned environments: Add 300–500 ml for 8+ hours in AC (reduces humidity).
Pregnancy / breastfeeding: Pregnant women need ~300 ml extra; breastfeeding ~700 ml extra.
Illness: Fever, diarrhea, and vomiting cause rapid dehydration. Increase intake and consider ORS.

Signs of Dehydration

Dark yellow urine: Most reliable indicator. Pale straw color means good hydration.
Persistent headache: Dehydration is one of the most common causes of afternoon headaches.
Fatigue and low energy: Even 2% dehydration can reduce performance by 20–25%.
Dry skin and lips: Chronic mild dehydration shows as dry, less elastic skin.
Dizziness when standing: Dehydration reduces blood volume, causing orthostatic hypotension.
Reduced urination: Less than 4–6 times a day means you need more fluids.

Common Hydration Myths Busted

Several popular beliefs about water intake are not scientifically supported:

"Drink 8 glasses a day" — Myth: No scientific study established this number. Needs depend on weight, activity, and climate.
"Clear urine means good hydration" — Partially false: Completely colorless urine may mean over-hydrating. Pale straw is ideal.
"Tea and coffee dehydrate you" — Myth: The water in tea and coffee still contributes to hydration.
"You need to drink when not thirsty" — Partially true: Thirst is a late indicator, especially in older adults.
"Cold water burns calories" — Negligible: About 8 calories per glass — insignificant.

Tips to Drink More Water

Keep a water bottle at your desk: Aim to finish a 1-litre bottle twice during work hours.
Use a reminder app: Set alarms every 1–2 hours to build the habit.
Drink before meals: A glass of water 20 minutes before each meal also helps with portion control.
Infuse your water: Add lemon, cucumber, mint, or fruit slices.
Start your day with water: Drink 300–500 ml immediately after waking.
Track your intake: Mark your bottle with time targets for visual accountability.