HydrationCalc: Daily Water

HydrationCalc is a daily water intake calculator. It estimates how much water to drink in a day from the three things that actually change the answer: your body weight, the activity you do and the climate you are in.

Most hydration advice gives everyone the same figure. Two litres, eight glasses, the same number for a 55 kg office worker in a cold month and for a 95 kg person training two hours in extreme heat. This water intake calculator builds the target from your own numbers instead, and it updates as you change them.

HOW THE CALCULATION WORKS
- Body weight sets the base, at 33 mL per kilogram of body weight
- Activity adds on top, by the hour: sedentary adds nothing, light adds 250 mL per hour, moderate 500 mL per hour, heavy 1000 mL per hour
- Climate adds a fixed daily amount: cold and temperate add nothing, hot adds 500 mL, extreme heat adds 1000 mL
- The three parts are added into one daily water target

WHAT YOU CAN DO
- Enter your body weight in kilograms and see the daily target straight away
- Choose one of four activity levels and set how many hours it lasts
- Choose one of four climate settings, from cold through to extreme heat
- Read your daily water intake in litres, millilitres and US fluid ounces together
- Watch the number recalculate live as you type, with nothing to submit
- Open the About screen for a one paragraph summary of the method
- Use it in light or dark theme, following your device setting

WHO IT IS FOR
- People who train or work physically and want a water target that reflects the session
- People living or working in heat, where an average figure falls short
- Anyone who wants a starting number for daily water intake instead of a guess

PRIVACY AND OFFLINE USE
HydrationCalc makes no network requests of any kind. There is no account, no sign up, no ads and no analytics. Everything you enter stays on your device and nothing is sent anywhere, so this water intake calculator works with no connection at all.

QUESTIONS
Does it need an internet connection? No. The whole calculation runs on your device.
Does it record what I drink during the day? No. It gives you the daily target to aim at, it does not log intake.
Which units does it use? Weight is entered in kilograms. The result is shown in litres, millilitres and US fluid ounces at once.
Where do the numbers come from? The app uses 33 mL per kilogram of body weight, an hourly allowance for activity and a fixed daily allowance for heat. The About screen sums up the method in one paragraph.
Does the target change if I train longer? Yes. The activity part is per hour, so the hours you enter move the total directly.

HydrationCalc is an informational water intake calculator, not medical advice. It does not diagnose or treat anything and it does not replace a health professional. Speak to a qualified professional about your own fluid needs.

Recent changes:
New app icon.