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Without Pro, you can log your drinks and see today, with a standard goal of 2,500 ml. Hydra Pro adds:

• your personal goal, from your weight, activity and climate;
• your full history: every day, week, month and year;
• CSV export of all your drinks or any period;
• reminders;
• My cups, your own amounts on Today.

Prices are in US dollars. The App Store shows the price in your own currency, which can differ by country. Payment is handled by Apple through In-App Purchase.

The yearly plan starts with 3 days free. The trial is offered once per Apple ID.

If you don’t cancel at least 24 hours before the trial ends, the yearly subscription starts and Apple charges you for the first year. After that, subscriptions renew automatically unless you turn them off at least 24 hours before the end of the current period.

Subscriptions are managed by Apple. On your iPhone, open Settings, tap your name, then Subscriptions, choose Hydra and tap Cancel Subscription. Deleting the app does not cancel a subscription.

You keep Pro until the end of the period you’ve paid for. When Pro ends, nothing is deleted: your drinks stay on your iPhone, and your full history comes back if you get Pro again. Lifetime is a one-time purchase, so there is nothing to cancel.

Hydra Pro belongs to your Apple ID. Hydra checks your purchases with the App Store each time it starts. If Pro doesn’t show up, for example on a new iPhone, open Hydra’s Settings › Hydra Pro and tap Restore at the bottom of the screen. Make sure you’re signed in with the Apple ID you used to buy Pro.

Refunds are handled by Apple; we can’t issue them ourselves. Go to reportaproblem.apple.com (opens in a new tab), sign in with your Apple ID, choose I’d like to › Request a refund, and select your Hydra purchase. If Apple approves the refund, Hydra Pro turns off in the app.

Hydra doesn’t just add up glasses. Every drink has a hydration factor, and what counts towards your goal is the amount multiplied by that factor:

net hydration = amount × factor

Studies show that coffee, tea, juice, soft drinks and sports drinks hydrate about as well as water, so they count in full. Milk and rehydration salts are retained better than water, so they count a little more. Alcohol makes your body lose water: beer counts only in part, wine adds nothing, and spirits take water away.

The factors come from published research (the Beverage Hydration Index, studies on coffee and on alcohol). You can see the sources in the app, in History.

Alcohol has a daily limit of 20 g, about one 500 ml beer. Up to that limit, alcoholic drinks count with their normal factor, so the water in a beer still hydrates you partly.

Past the limit, the water in alcoholic drinks no longer counts, only the alcohol does:

For example, a first 500 ml beer adds about 300 ml to your day; a second one takes about 200 ml away. Today then shows how much water you need to drink to offset the alcohol. In short: Hydra counts water, not beer.

With Hydra Pro, Hydra suggests a personal goal for what you drink each day, from your profile:

The total is rounded to the nearest 50 ml and kept between 1,500 and 5,000 ml. For example, 70 kg, sex not set, slightly active, temperate climate: 2,310 + 200 = 2,510, so the goal is 2,500 ml. That is also the standard goal Hydra uses without Pro.

The values are based on the European (EFSA) and US (National Academies) recommendations and on newer research on water turnover. Hydra shows the breakdown of your goal in the app, and you can always set your own goal instead.

Reminders are part of Hydra Pro. Turn them on in Settings › Reminders. You choose:

• Remind me after 1, 1.5, 2 or 3 hours without a drink;
• Active hours, 08:00–22:00 by default. There are no reminders outside them.

Every drink you log restarts the timer. On a day you haven’t logged anything yet, the first reminder comes at the start of your active hours. Once you reach your goal for the day, reminders stop until the next day.

Each reminder has an Add 250 ml of water button (8 oz in imperial units): touch and hold the notification to log a glass without opening Hydra.

Not getting reminders? Check that notifications are allowed for Hydra in the iOS Settings app, and that a Focus mode isn’t silencing them. Opening Hydra refreshes the upcoming reminders.

Export is part of Hydra Pro.

• Everything: Settings › Export data.
• One period: in History, tap the share button to export the period on screen: a day, week, month, six months or a year.

You get a CSV file you can open in Numbers, Excel or Google Sheets, with one row per drink: day, time, drink, amount_ml, factor and net_ml. Amounts are always in millilitres. The file is created only when you export, and goes only where you send it.

Not yet. Apple Health and iCloud sync are planned as optional features. Until then, all your data stays on your iPhone.