How much water should I drink a day? Calculate it by body weight
Short answer: Multiply your body weight in kilograms by about 30–35 ml. A practical middle value is 33 ml per kg: 60 kg → about 2.0 L, 70 kg → about 2.3 L, 80 kg → about 2.6 L a day from drinks. Treat it as a starting point, not a rule.
Quick table (33 ml per kg)
| Body weight | Daily goal | 250 ml cups |
|---|---|---|
| 50 kg (110 lb) | 1.65 L | about 7 |
| 60 kg (132 lb) | 2.0 L | 8 |
| 70 kg (154 lb) | 2.3 L | about 9 |
| 80 kg (176 lb) | 2.65 L | about 11 |
| 90 kg (198 lb) | 3.0 L | 12 |
Why "8 glasses" is only a rough rule
Eight 250 ml glasses is 2 L, which fits a person of about 60 kg. Larger bodies, hot weather and exercise need more; smaller bodies need less. Food also supplies water, so this goal is for what you drink.
When to drink more
- Hot or humid days, and after sweating from exercise.
- Illness with fever, vomiting or diarrhea.
- Pregnancy or breastfeeding.
If you have kidney or heart conditions, follow your doctor's fluid advice instead of a formula.
How to actually reach it
Split the goal over your waking hours. With 16 waking hours and a 2.3 L goal, you need about 145 ml per hour. Gulply suggests a goal from your weight, lets you type your own, and reminds you only when you fall behind that pace. Log +250 ml from the notification or widget in one tap.