Drink Water Calculator
Drink water calculator works out Fluid to drink and Baseline requirement from Method, Units and Age. The default figures on this page give fluid to drink of 2,960 mL/day; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
3 steps
- DRI band: Adults 19 and over. Adequate intake for total water = 3.7 L/day.
- Water in food supplies the rest, so the amount to drink = 3700 x 0.8 = 2960 mL/day.
- Total to drink = 2960 mL/day = 2.96 L = 12.5 eight-ounce cups
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
4 sources
Keep this result
Save it, change one figure, then compare the two
The calculation stays free. Save this scenario, adjust one assumption, save that too, and put them side by side to see exactly what the change costs you. A free account keeps 5 scenarios and 2 comparisons; Personal makes both unlimited and adds exports and private links. Nothing is saved unless you press Save.
What the drink water calculator calculates
Daily fluid requirement from the National Academies Dietary Reference Intakes, a millilitres-per-kilogram rule or the Holliday-Segar maintenance formula, with additions for exercise, heat and pregnancy.
How to use this drink water calculator
Enter Method, Units, Age and Sex. Fluid to drink updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Fluid to drink, Baseline requirement and Added for exercise.
The method follows Institute of Medicine (now NASEM), Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate, National Academies Press, Mayo Clinic, Water: how much should you drink every day?, Holliday MA & Segar WE, The maintenance need for water in parenteral fluid therapy, Pediatrics 1957;19:823-832 - the 100/50/20 mL/kg rule and American College of Sports Medicine position stand, Exercise and Fluid Replacement, Med Sci Sports Exerc 2007;39:377-390 - sweat rates typically 0.5 to 2.0 L per hour, replaced according to individual sweat loss.
DRI adequate intake, man of 30 example
With Method: dri, Age: 30, Sex: male, Pregnancy or breastfeeding: none, the calculator returns Total water including water in food (DRI method): 3.7, Baseline requirement: 2960, Fluid to drink: 2.96. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Fluid to drink, Baseline requirement and Added for exercise. The inputs you can vary are Method, Units, Age, Sex, Pregnancy or breastfeeding and Body weight.
Understanding Fluid to drink, Baseline requirement and Added for exercise
These are population reference intakes, not a prescription. Heart failure, kidney disease, liver disease and some medications require a fluid restriction rather than a target, and drinking far above requirement can cause dangerous hyponatraemia. Ask a clinician before changing fluid intake for a medical reason.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How can I calculate how much water I should drink?
Daily fluid requirement from the National Academies Dietary Reference Intakes, a millilitres-per-kilogram rule or the Holliday-Segar maintenance formula, with additions for exercise, heat and pregnancy. Open “How this is worked out” beside the result to see each step for your own figures.
What drinks hydrate better than water?
Daily fluid requirement from the National Academies Dietary Reference Intakes, a millilitres-per-kilogram rule or the Holliday-Segar maintenance formula, with additions for exercise, heat and pregnancy. On this page it is computed from Method, Units and Age and shown as Fluid to drink, Baseline requirement and Added for exercise.
How much water should a 200lb man drink a day?
On the figures this page opens with — age 30 years — the fluid to drink is 2,960 mL/day. No single number fits everyone: change any figure above and the answer updates as you type, with each step of the arithmetic beside it.
How much water should I drink according to my age?
It needs Method, Units, Age, Sex, Pregnancy or breastfeeding and Body weight. Nothing else is required, and the figures stay in your browser.
How much water should I drink based on my weight?
The result gives Fluid to drink, Baseline requirement, Added for exercise, Added for heat, altitude or illness, Total water including water in food (DRI method) and Reference band used, each labelled with its unit so the figure can be read on its own.
What information do I need for the drink water calculator?
You need Method, Units, Age, Sex, Pregnancy or breastfeeding, Body weight, Extra pounds and Millilitres per kilogram per day. The page opens with default figures that give fluid to drink of 2,960 mL/day, so you can see the scale before entering your own.