How Much Water Should You Drink Per Day? The Real Answer

The "8 Glasses a Day" Myth

You've heard it a thousand times: drink 8 glasses of water a day. But where did this number come from?

It traces back to a 1945 US Food and Nutrition Board recommendation — which actually said most of that water comes from food. The "8 glasses" figure was never meant to apply uniformly to everyone.

The Science-Based Formula

The most accurate way to calculate hydration needs:

Daily water (ml) = Body weight (kg) × 35ml

For a 70kg person: 70 × 35 = 2,450ml (about 2.5 liters)

Then add adjustments:

• Exercise: Add 500ml per hour of moderate activity
• Hot climate: Add 500–750ml on hot Pakistani summer days (35°C+)
• Breastfeeding: Add 700ml extra
• Illness/fever: Add 500ml per degree above normal temperature

Signs You're Dehydrated

• Urine darker than pale yellow
• Headaches, especially afternoon headaches
• Fatigue and brain fog
• Dry mouth and lips
• Constipation
• Dizziness when standing

Quick test: Check your urine color. Pale yellow = well hydrated. Dark yellow/amber = drink more water immediately.

Does Tea and Coffee Count?

Yes — despite common belief, moderate caffeine consumption (up to 400mg/day, about 4 cups of chai) has a mild diuretic effect but contributes net fluid to your body. Your afternoon chai absolutely counts.

Juices, soups, and water-rich foods (cucumbers 95%, watermelon 92%) also count toward total fluid intake.

Optimal Hydration Schedule

Use Our Water Calculator

Get your exact personalized water intake target with our Water Intake Calculator. Track your daily intake with our Wellness Tracker — free, no signup required.