How to use it
Enter your weight
Type your body weight and pick kilograms or pounds. Switching the toggle converts the number for you.
Add exercise minutes
Enter how many minutes you usually spend exercising each day. Leave it at zero if it is a rest day.
Read your target
The estimate updates instantly in liters, with cups and US fluid ounces shown for easy reference.
About the water intake calculator
This calculator starts from a common rule of thumb: about 33 ml of water for every kilogram of body weight. It then adds roughly 350 ml for each 30 minutes of exercise to account for fluid lost through activity. The figure is a gentle starting point, not a strict rule — food, drinks, climate, pregnancy and individual health all change how much you actually need. Listen to your thirst and the color of your urine as everyday guides. This is for general guidance only and is not medical advice; talk to a clinician if you have a condition that affects fluid balance.
Questions
Is anything uploaded?
No. The whole calculation runs in your browser and nothing you type is sent anywhere or stored.
How is the estimate worked out?
Baseline is your weight in kilograms multiplied by 33 ml, plus your exercise minutes divided by 30, multiplied by 350 ml. One cup is treated as 250 ml and one US fluid ounce as 29.57 ml.
Should I follow this exactly?
Treat it as a friendly starting point rather than a target to force. Your real needs shift with heat, activity, diet and health, so adjust to how you feel and check with a professional when in doubt.