Home › Blog › How much water should I drink a day?
How much water should you drink a day if you weigh 80 kg?
At 80 kg (176 lb), aim for about 2.6 litres (89 fl oz) a day if you mostly sit, and more on active or hot days.
Updated October 17, 2026
2.6 litres a day
About 89 fl oz, 11 glasses or 5.5 bottles of 500 ml, if you mostly sit. More if you're active or it's hot.
By activity and weather
| Your day | Normal day | Hot day |
|---|---|---|
| Mostly sitting | 2.6 L (89 fl oz) | 3.1 L (106 fl oz) |
| Lightly active | 3.0 L (101 fl oz) | 3.5 L (118 fl oz) |
| Very active | 3.3 L (113 fl oz) | 3.8 L (130 fl oz) |
These come from 33 ml per kilogram of body weight (80 × 33 = 2.6 L), plus 350 ml for a lightly active day or 700 ml for a very active one, and 500 ml more in the heat.
That falls between the US National Academies' general figures for women (2.2 L) and men (3.0 L) from drinks.
Spread it across your day
5.5 bottles is easier to picture than 2.6 litres. The simplest plan is one 500 ml bottle about every 3 hours between 7 am and 9 pm, starting with a glass when you wake up. Steady drinking also suits your kidneys, which can only clear about a litre an hour.
Training today? The American College of Sports Medicine suggests about 0.4–0.8 litres for each hour of exercise, on top of your daily amount.
Try other numbers
Change the weight, activity or weather to see your exact amount.
Questions people ask
Is 3.6 litres too much at 80 kg?
Spread across a day, no. Healthy kidneys can handle far more than that. What matters is pace: drinking more than about a litre an hour for several hours is what gets risky.
Do coffee and tea count toward my water?
Yes. A study that gave regular coffee drinkers four cups a day found they stayed just as hydrated as when they drank the same amount of water. Water is still the best default because it has no sugar or caffeine.
Should I drink more if I take creatine?
A sensible buffer is about 500 ml (17 oz) on top of your daily amount, plus a glass with each dose. That puts you at about 3.1 litres (106 fl oz).
Sources
Keep reading
Get Waterbreak
The apps you can't put down stay locked until you drink. Free on iPhone and Android, in 13 languages.