FOODMANAC · KNOW YOUR NUMBERS
Water Intake Calculator
Explore a weight-based fluid estimate with clearly labeled, adjustable activity and climate allowances.
Your details
YOUR ESTIMATE
Start with your details
Enter your measurements to see the calculation and its assumptions.
Connect your numbers to real food
Search Foodmanac’s existing food database. Choose the correct preparation and compare its recorded nutrient basis with a portion you actually eat.
How to use this water intake calculator
The base rule comes from nutrition-support guidance, not a universal healthy-adult hydration equation. Added allowances default to zero because sweat losses vary. Count all fluid sources. General population water reference values also include water in food; they are not amounts to drink on top of meals. This tool is not for fluid restriction or endurance hydration.
Formula and assumptions
Base total fluid = 30–35 mL × body weight in kg. Add your selected activity minutes ÷ 60 × mL/hour allowance and your chosen climate allowance.
Example calculation
At 70 kg, the base estimate is 2.10–2.45 L/day. Choosing 60 minutes, 400 mL/hour and 250 mL extra gives an illustrative 2.75–3.10 L/day.
Frequently asked questions
Are the climate adjustments scientifically fixed?
No. You enter a planning allowance; there is no validated universal hot-weather correction here.
Should I force myself to drink the result?
No. An estimate does not override thirst, symptoms or individual clinical advice.
What does mL/hour mean?
It means millilitres for each hour of activity. For arithmetic illustration, 400 mL/hour for half an hour adds 200 mL. This is not a recommendation to use that allowance.
What should I enter for hot weather if I am unsure?
Leave the optional amount at zero. There is no fixed correction that works for everyone. Heat, sweating, clothing and work conditions differ.
Does the result tell me whether I am dehydrated?
No. Body weight and chosen allowances cannot diagnose hydration status.
Should I add this amount to what I already drink?
No. Count fluid already consumed toward the estimate. It is a rough planning total, not an additional drinking instruction.
Why are the optional allowances zero by default?
The calculator cannot measure your sweat losses. Zero means no extra allowance was selected; it does not mean activity or heat never increases your needs.
What if I do not know which number to enter?
Read the explanation below each field. The initial values are examples, not your measurements. Use your scale or tape for body measurements. For a calorie budget, start with the Calorie or TDEE calculator. Optional water allowances can stay at zero.
Can I switch between kilograms and pounds or centimetres and inches?
Yes, where body measurements are used. Changing the unit selector converts the entered values. Imperial height is total inches: 5 feet 9 inches is 69 inches, not 5.9.
Who is this calculator intended for?
Generally healthy adults aged 20–78 who are not pregnant or breastfeeding. It is not intended for children, eating-disorder recovery, medically prescribed diets or fluid restrictions.
Why can another calculator give a different result?
Tools may use different equations, activity assumptions, unit conversions or rounding. Compare the method and inputs before comparing the result. None of these estimates is an exact measurement.
How do I save my result?
Calculate first, then choose Download PNG or Print / Save PDF. The export includes the inputs, results, explanation, method and references. Your site logo is included when configured; otherwise a Foodmanac wordmark is used.
Are my measurements sent to Foodmanac?
This plugin calculates in your browser and does not send your measurements. Food search sends the food name to the website. Other site plugins may have their own analytics or privacy behavior.
Sources and methodology
Source-backed equations are distinguished from Foodmanac planning presets. No result is an exact measurement or a medical prescription. Content version: 1.1.0.
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