A goal made for you
A few quick questions about your weight, activity, climate and life stage, and Rainu estimates a daily goal from published guidance. You can always see the maths.
Water tracker for iPhone
Drink more water.
Drink more water.
Meet Droplee.
Your daily water goal, backed by science. Log any drink in one tap, and let a little drop with big feelings keep you on track.
Free · No account · iPhone with iOS 17 or later
What's inside
Small habit, built with care
Everything in Rainu is designed to make the next glass of water easy, without nagging.
Every drink counts
Water, coffee, tea, juice, milk and soda, each counted by its typical water content. Sizes that make sense, like a 40 ml espresso, and quick-add buttons for your usual glass.
Reminders that respect your sleep
A good-morning nudge, then gentle reminders through your day. Smart mode skips them when you're on pace, and they stop before bedtime so nothing buzzes while you wind down.
Widgets & Siri
Log a drink right from your Home Screen, Lock Screen or StandBy, or just ask Siri to "Log 250 ml in Rainu". The app and widgets stay in sync.
Works with Apple Health
With your permission, drinks are saved to Apple Health as water (and caffeine for coffee). Undo a drink in Rainu and it's removed from Health too.
Your own target or limit
If a healthcare professional has given you a daily fluid target or limit, enter it and Rainu follows it. In limit mode, Rainu never nudges you to drink more.
Private by design
No account, no sign-up, no ads, no analytics. What you log stays on your iPhone. We don't run servers that could see it.
A look inside
Bright, calm, and quick
Backed by science
How your goal is calculated
Rainu starts from the European Food Safety Authority's adequate intake for water from drinks, then adjusts it for you. The result is rounded to the nearest 50 ml and kept between 1,200 and 4,000 ml.
- Base: 1,600 ml (female) or 2,000 ml (male). EFSA, Dietary Reference Values for water, 2010.
- Body weight: a small adjustment above or below a reference weight, capped at ±500 ml. Yamada et al., Science, 2022.
- Exercise: about 500 ml per hour of activity. American College of Sports Medicine position stand, 2007.
- Hot climate: +500 ml. Pregnancy: +300 ml. Breastfeeding: +700 ml (EFSA).
These are general estimates for healthy adults, not medical advice. Needs vary: drink to thirst, and follow your doctor if they've given you a target or limit.
Example daily goal
2,300 ml
- Base EFSA 2010
- 2,000 ml
- Weight, 75 kg Yamada 2022
- +70 ml
- Exercise, 30 min ACSM 2007
- +250 ml
- Heat
- +0 ml
2,320 ml, rounded to 2,300 ml. Your numbers will differ.
Questions
Good to know
Is Rainu free?
Yes. Rainu 1.0 is free, with no ads and no in-app purchases.
Do I need an account?
No. There's no sign-up and no login. Your data is stored on your iPhone.
Why does coffee count?
Coffee is mostly water. In moderate amounts, studies show it hydrates almost as well as water, so Rainu counts it at 99% of its volume. If you allow it, Rainu also saves the caffeine to Apple Health.
Is Rainu a medical app?
No. Rainu is a wellness app, not a medical device. It doesn't diagnose or treat anything. If you have a health condition or a fluid target or limit from your doctor, follow their advice.
Droplee is getting thirsty
Rainu is coming soon to the App Store for iPhone.