Human Calculators
Daily water intake calculators for adults — men, women, elderly, weight-based, and weather-based.
Most popular in Human Calculators
Adult Daily Water Intake
Personalized daily water target for healthy adults, adjusted for weight, activity, and climate.
Open calculatorElderly Water Intake (65+)
Daily hydration target for older adults, with a safe minimum floor and climate adjustments.
Open calculatorWater Intake for Weight Loss
Higher-end daily target with pre-meal water boost that supports satiety and weight loss.
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Menstrual Cycle Water Intake
Increased water target during your period to reduce cramps, headaches, and bloating.
OpenCold Weather Water Intake
Winter hydration target adjusted for indoor heating and outdoor cold exposure.
OpenOffice Worker Water Intake
Desk-job hydration target with coffee/tea offset and air-conditioning add-on.
OpenIntermittent Fasting Water Calculator
16:8, 20:4, and OMAD fluid targets.
OpenOMAD Water Intake
One-meal-a-day hydration plan.
Open24-Hour Water Fast Calculator
Fluid and electrolytes for a 1-day fast.
Open3-Day Water Fast Calculator
Extended fast fluid and mineral protocol.
OpenNight Shift Nurse Water Intake
12-hour night-shift hydration plan.
OpenTruck Driver Water Intake
Long-haul driving hydration target.
OpenGamer / Streamer Water Intake
Marathon-session hydration for gaming.
OpenCall Center Agent Water Intake
Voice-friendly hydration for talk-heavy jobs.
OpenTeacher Water Intake
Classroom-day hydration for teachers.
OpenSimple, accurate, personalized
Pick your calculator
Choose the one that matches your situation from the grid above.
Enter a few details
Weight, activity, climate, species — takes under 30 seconds.
Get your target
A research-backed daily target plus an hourly schedule.
Learn the science behind human calculators
Read our in-depth guides for research-backed context on every calculator here.