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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Hot Weather / Summer Water Intake
Daily water target adjusted for temperature, humidity, and hours spent outdoors in the sun.
OpenDehydration Risk Check
Quick self-check: score your urine color, thirst, and symptoms to get an immediate rehydration recommendation.
OpenSick-Day & Fever Rehydration
Adjust your daily water target for fever, vomiting, or diarrhea — with an ORS recommendation when losses are high.
OpenCoffee Water Balance
See how much extra plain water you need on top of your daily coffee habit.
OpenAlcohol Rehydration Calculator
Estimate how much water to drink to offset alcohol's diuretic effect and cut hangover severity.
OpenFlight & Travel Water Intake
Hydration target for air travel — accounts for dry cabin air, flight length, and alcohol.
OpenKeto & Low-Carb Water Intake
Elevated daily target for keto or low-carb diets — includes sodium and electrolyte guidance.
OpenHangover Rehydration
Post-drinking rehydration protocol — matched to drinks consumed and symptom severity.
OpenFasting Water Intake
Fluid and electrolyte plan for intermittent fasting, OMAD, 24-hour, and extended fasts.
OpenRamadan Water Intake
How to space fluids between iftar and suhoor to stay hydrated across a long fasting day.
OpenDiabetic Water Intake
Daily fluid target for people with diabetes, adjusted for glucose control and climate.
OpenNight Shift & Shift-Worker Hydration
Front-loaded hydration plan for night shift and rotating shift workers.
OpenSimple, accurate, personalized
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Weight, activity, climate, species — takes under 30 seconds.
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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.