How much water do you really need?
The old “eight glasses a day” rule is a handy slogan but a rough one. A more personal estimate scales with your bodyweight — roughly 33 ml of fluid per kilogram — then adds extra for exercise and hot weather. For many adults that works out between 2 and 3 litres a day from all sources.
Two important points: this total counts all drinks, not just plain water, and water-rich foods like fruit, vegetables, and soup chip away at the goal too. Your true need shifts day to day with activity, temperature, altitude, illness, and even how salty your meals are.
Signs you’re not drinking enough
The easiest gauge is your urine — pale and plentiful is the target. Watch for:
- Dark yellow urine or going noticeably less often than usual.
- Headaches, fatigue, or trouble concentrating in the afternoon.
- Dry mouth, lips, or skin and feeling thirsty before meals.
- Light-headedness when you stand up, or muscle cramps after exercise.
Mild dehydration is common and easy to fix — most people simply forget to drink during a busy day rather than truly running short.
Tips to drink more
- Keep a refillable bottle in sight; we drink what is in front of us.
- Pair water with existing habits — a glass with every coffee and meal.
- Front-load earlier in the day so you are not gulping litres before bed.
- Flavour it with lemon, cucumber, or mint if plain water bores you.
- Log each glass so you can actually see your progress.
That last one is where an app helps. Swoodie has one-tap hydration logging built right next to your meals — tap to add a glass and watch your daily goal fill up, with gentle reminders if you fall behind. While you are setting goals, the TDEE calculator covers the calorie side of the equation.
Frequently asked questions
How much water should I drink a day?
A common starting point is about 33 ml of fluid per kilogram of bodyweight, then add more for exercise and hot weather. For many adults that lands between 2 and 3 litres a day, but your real needs depend on activity, climate, and the food you eat.
Does coffee, tea, and food count toward water intake?
Yes. Almost all drinks count toward your total fluid intake, and water-rich foods like fruit, vegetables, soup, and yoghurt contribute a meaningful share too. Despite its reputation, moderate coffee and tea still hydrate you on balance.
How do I know if I'm drinking enough?
Pale, straw-coloured urine and rarely feeling thirsty are good signs you are well hydrated. Dark urine, headaches, fatigue, dizziness, or a dry mouth can signal you need more fluids.
Should I drink more water on workout days?
Yes. You lose fluid through sweat, so add roughly 350–500 ml for every 30 minutes of intense exercise, and more in heat. Drink before, during, and after training, and consider electrolytes for long or very sweaty sessions.
Can you drink too much water?
Rarely, but yes. Drinking far more than you need in a short time can dilute blood sodium (hyponatraemia), which is dangerous. Spread your intake across the day and let thirst and urine colour guide you rather than forcing large volumes at once.
This tool provides general guidance for healthy adults and is not medical advice. People with kidney, heart, or liver conditions — or anyone on fluid restrictions — should follow the specific fluid guidance of their doctor.