The honest number
The famous “8 glasses a day” was never a scientific law — but as a rough landing zone it isn't bad. Most adults do well on about 2 to 2.5 litres of fluid a day (roughly 6–8 decent glasses), and notably that includes the water in coffee, tea, milk and food. Fruit, vegetables and soup can quietly cover 20% of your needs. Your body also ships with an excellent built-in gauge: thirst, plus urine color — pale straw yellow means you're fine; apple-juice dark means drink up.
When you need more than baseline
- Exercise: add roughly 500 ml–1 litre per hour of sweaty training.
- Heat: summer, saunas and radiators all raise the bill.
- Illness, altitude, pregnancy and breastfeeding all push requirements up.
- Fasting windows: if you do 16:8, remember a lot of daily water normally arrives with meals — skip breakfast and you should drink some of it back deliberately.
Water and weight loss: useful, not magic
Water won't melt fat, but it earns its place in a weight-loss toolkit three modest, real ways:
- Thirst wears a hunger costume. Mild dehydration often reads as snackiness. A glass of water before raiding the cupboard settles the question for free.
- Pre-meal water helps portions. A glass before meals adds a bit of fullness — studies on dieters have found it nudges intake down without any willpower spent.
- It replaces liquid calories. Every water that stands in for a juice or soda is 100–150 kcal that never needs burning. This is the single biggest hydration win for a calorie deficit.
Bonus sanity note: drink a lot of water today and the scale may go up tomorrow — water has weight. It's the good kind of heavier; the trend line knows the difference.
Making hydration automatic
- Anchor it to habits you already have: a glass on waking, one with every meal, one when the kettle goes on. Four anchors ≈ most of the day handled.
- Keep water visible. A full bottle on the desk beats a tap in another room — friction works in both directions.
- Make it nicer: cold, sparkling, a slice of lemon. You'll drink more of what you like; hydration doesn't have to be penance.
- Count something. A glass tally turns “did I drink enough?” from a guess into a glance.
Water tracking in Calfit
Calfit puts a one-tap water counter right on the home screen — tap, glass logged, progress bar fills toward your daily glasses. Hydration feeds into your daily health score alongside meals, movement and sleep-friendly gentle reminders, so “5 of 8 glasses” sits right next to your calories left. Small thing, honestly kept — which is rather the whole Calfit philosophy.