Water Intake Calculator
Adjust the inputs below. Results update as you type.
How it works
General rule: body weight (lb) / 2 = ounces per day. Add 12 oz for every 30 minutes of exercise. Hot or humid climate: add 16–24 oz. Pregnancy: add ~10 oz; breastfeeding: add ~13 oz. 80% of hydration can come from beverages; 20% from food (fruits and vegetables). Urine color is the best practical hydration indicator: pale yellow = well hydrated; dark yellow = drink more.
Input guidance
- Confirm date/time/unit settings before comparing outputs.
- If a task has optional fields, run both with and without them to understand impact.
- Save scenario variants when making practical decisions.
The formula
A common estimate is about 30–35 ml of water per kilogram of body weight per day, adjusted up for exercise, heat, and individual needs.
Worked example
A 70 kg person needs roughly 70 × 33 ml ≈ 2.3 liters per day, more on hot days or with intense activity.
More examples to test
- Quick-pass example: run default assumptions for a first estimate.
- Refined example: update one assumption at a time to isolate impact.
How to interpret results
Use outputs as operational estimates and pair them with local constraints, business rules, or provider requirements.
When this can be inaccurate
Utilities can miss local policy details, special-case rules, and environment-specific constraints.
Change history
- July 2026: Published hydration target path with activity adjustment notes.
Site-wide corrections also appear on the corrections log.
Track calories, macros, and fitness progress
General wellness resource.
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General recommendation, not professional advice.
Frequently asked questions
How much water should I drink?+
Estimates suggest roughly 30–35 ml per kg of body weight daily, but needs vary with activity, climate, and health. Thirst is a useful guide.
Does food count toward hydration?+
Yes. Fruits, vegetables, and other foods provide significant water, so total fluid needs are not met by drinks alone.
Can I drink too much water?+
Rarely, but excessive intake in a short time can dilute blood sodium (hyponatremia). Spread intake through the day rather than overloading.
Why are outputs slightly different from another tool?+
Different tools can use different rounding rules, default assumptions, and treatment of edge cases.
How can I improve estimate reliability?+
Use verified inputs from real records and re-run calculations after major assumption changes.
Guided next steps
Want the full workflow? Use this calculator inside a step-by-step guide.