Health & Fitness
Water Intake Calculator
Water Intake Calculator is a browser-based calculator tool on CalcToolsBase. Estimate a daily water intake target from your body weight and activity level. To use it, enter your values and view the result directly in your browser — no signup and nothing to install.
Use Water Intake Calculator to estimate your daily water intake: give it your weight and activity level, press Calculate, and read off a daily target in litres and glasses — all worked out on your device.
About this calculator
Water Intake Calculator is built to estimate your daily water intake without a server round-trip. Provide your weight and activity level and it uses your weight and activity level to produce a daily target in litres and glasses, instantly and entirely in your browser, which makes it handy for quick checks and repeat runs.
Real hydration needs change with climate, sweat, diet, and health, and food also provides water. Use thirst and urine colour as practical guides alongside this estimate.
How to use
- Enter your body weight in kilograms for the water target.
- Choose your typical activity level.
- Press Calculate to see a daily water target.
- Drink more in heat or during intense exercise.
Why use Water Intake Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Educational
Uses common estimation formulas for educational purposes. Results are not medical advice and should not replace professional guidance.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Clear about formulas used and their limits, with disclaimers where they matter.
Common uses
Water Intake when tracking progress over time
Water Intake alongside a workout plan
Water Intake for everyday fitness check-ins
Water Intake for comparing before-and-after
Water Intake when logging weekly numbers
Water Intake when learning what a metric means
Technical notes
Water Intake Calculator estimates daily water need from body weight (roughly 30–35 ml per kg).
These are general-population estimates and not a substitute for advice from a qualified clinician.
Because it runs locally, results appear instantly with no server round-trip.
FAQ
How much water should I drink daily?
A common baseline is about 35 ml per kg of body weight, so 70 kg is roughly 2.4–2.5 litres, with more added for activity, heat, or illness.
Does activity change my water needs?
Yes — sweating during exercise raises fluid loss, so active and very active days need extra water beyond the resting baseline.
Does food count toward hydration?
Yes. Many foods, especially fruit and vegetables, contain water and contribute to your total daily intake along with all beverages.
Does the Water Intake Calculator send my data to a server?
No. The Water Intake Calculator runs entirely in your browser — your inputs never leave your device, and nothing is uploaded or stored.
Worked example
A common rule of ~35 mL per kg gives a 70 kg adult 70 × 35 = 2,450 mL (~2.5 L)/day; needs rise with heat and activity.