Daily Water Intake Calculator for Health and Hydration

This calculator personalizes a daily drinking-water target using widely referenced rules of thumb. It starts with body weight, layers on activity time, adjusts for climate, and considers pregnancy or breastfeeding when selected. Results display in liters by default and also show cups and fluid ounces for convenience. Think of the target as your practical starting point for the day rather than a strict quota.

Good hydration supports alertness, temperature control, digestion, skin appearance, and exercise performance. Your needs vary through the week. Hot or dry air, long workouts, high-altitude trips, salty meals, caffeine, and alcohol can all nudge requirements upward. Use the activity and climate fields to reflect days that are sweatier or longer than average. If your urine is consistently pale straw and you feel well, you are likely close to your mark.

• Carry a bottle you enjoy using and refill it on autopilot.
• Spread intake across the day to avoid stomach slosh.
• Include water-rich foods like soups, fruit, and vegetables.

The number shown is drinking-water only. Beverages such as tea, coffee, and milk hydrate too, though alcohol does not count toward your target. People with kidney, heart, or endocrine conditions should follow medical guidance rather than general calculators. If you receive fluid restrictions or diuretic prescriptions, prioritize those instructions.

The tool uses a simple baseline and sensible add-ons:

• Baseline: 35 mL per kg of body weight per day.
• Exercise: +350 mL for every 30 minutes of activity.
• Climate: +0 mL (temperate), +350 mL (warm), +700 mL (hot).
• Pregnancy: +300 mL; Breastfeeding: +700 mL.

Example (metric): 70 kg, 30 minutes, warm climate, none selected → 70×35 = 2450 mL; +350 mL for activity; +350 mL for warmth = 3150 mL ≈ 3.15 L. The tool also displays a flexibility band of ±10% to reflect day-to-day variation. Results appear in liters plus an approximate conversion to cups (240 mL) and US fluid ounces.