How Much Water Should You Drink? A Practical Hydration Guide
Hydration affects energy, focus, digestion, and exercise performance. The old 'eight glasses' rule is a starting point, but your real needs depend on size and activity.
Here's a simple way to estimate intake and check you're getting enough.
The formula
A common estimate is 30–35 ml of water per kg of body weight per day, plus extra for exercise and heat.
Adjust for activity
Add roughly 350–700 ml for every hour of exercise, and more in hot or humid conditions.
Check your hydration
Pale-yellow urine and steady energy are good signs. Dark urine and headaches suggest you need more.
Related calculators
Frequently asked questions
Can I drink too much water?
Rarely, but excessive intake in a short time can dilute sodium — spread intake across the day.
Do coffee and tea count?
Mostly yes; their mild diuretic effect is offset by the fluid they contain.
This tool provides educational information and is not intended to replace professional medical advice.