Water Intake by Weight Calculator — Daily Water Needs 2026

The most accurate method for calculating daily water intake is based on body weight. The general guideline is 0.5–1 oz of water per pound of body weight per day (or 30–35 ml per kg). A 150 lb (68 kg) person needs approximately 75–150 oz (2.2–4.4 liters) of water daily. This baseline increases with exercise, heat, illness, pregnancy, and breastfeeding. Our weight-based water calculator gives you a personalized daily target in both oz and ml. No sign-up required — your data never leaves your browser. Works instantly on desktop, tablet, and mobile. Completely free with no daily usage limits, no watermarks, and no account needed. Trusted by students, professionals, and businesses worldwide. FixFlowHub is a browser-based toolbox with 120+ free utilities covering PDF, image, text, calculator, and productivity tools.

Frequently Asked Questions

How much water should I drink based on my weight?

A general guideline is 0.5 oz per pound of body weight (or 30 ml per kg) as a minimum. For a 150 lb person: 75 oz/day minimum. Athletes and active people need more.

Is the 8 glasses a day rule accurate?

The 8×8 rule (8 glasses of 8 oz = 64 oz/day) is a rough guideline. Individual needs vary significantly based on weight, activity level, climate, and health status.

Does coffee and tea count toward daily water intake?

Yes — caffeinated beverages contribute to hydration, though coffee has a mild diuretic effect. Plain water is best, but coffee and tea count toward your total fluid intake.

Related free tools

More free calculators