Water Intake Calculator
🇳🇿 New Zealand version
In New Zealand the shared NHMRC and Ministry of Health reference values are 2.6 L of drinks a day for men and 2.1 L for women, and Health NZ gives a simple guide of 8 to 10 cups. This page starts your goal from those figures and adds a weight-based target with a drink log.
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New Zealand rules and figures
- NHMRC and the Ministry of Health share one set of reference values for both countries: 2.6 L of drinks for men, 2.1 L for women, each day.
- Health NZ offers a simple guide of 8 to 10 cups, which it puts at 2 to 2.5 L of fluid a day.
- Food adds to total water, giving 3.4 L for men and 2.8 L for women, so a log of drinks alone is expected to come in lower.
- The New Zealand page begins with weight in kilograms and shows volumes in millilitres, with 70 kg as the sample weight.
Sources: NHMRC and Ministry of Health: Nutrient Reference Values, water (checked 2026-11-08); Health NZ: Drinking enough fluids (checked 2026-11-08)
How the water intake calculator works
The weight-based target multiplies 35 mL per kilogram by activity, climate and the other settings, and never exceeds 50 mL per kilogram. Your daily goal is a separate setting that begins at the reference value for the gender you choose, or at the mid-point until you choose one.
85 kg × 35 = 2,975 mL; × 1.05 (male) × 1.25 (Moderate) = 3,905 mL; Optimal 4,295 mL is cut to the 85 × 50 = 4,250 mL ceiling
- The reference values cover drinks alone, 2.6 L for men and 2.1 L for women. Counting food too, total water rises to 3.4 L and 2.8 L.
- Health NZ puts it simply as 8 to 10 cups, or 2 to 2.5 L, of fluid a day.
- Until gender is set on the Settings tab, the goal sits at the mid-point of 2,350 ml.
- Counting uses hydration values, so coffee at 0.8 and fruit juice at 0.85 add less than their full volume.
- Kilograms and millilitres are the starting units, and a unit you pick is remembered.
How to use the water intake calculator
- Add your weight and gender. In Settings, enter weight in kilograms and choose male or female. That choice sets which reference value your goal starts from.
- Pick activity and climate. Choose how active you are and what the weather is like. Altitude is optional and only matters above 2,500 m.
- Record each drink. Select the drink, enter its volume in millilitres and add it. Add a note if you want one.
- Look at the reference amounts. The Analysis tab lists Minimum, Recommended, Optimal and Max Safe for your weight.
- Save or share. Share Report copies the day's summary, and Export Data downloads your profile, goal and log as JSON.
Example: An 85 kg man aged 30, Moderate activity, Temperate climate
Male adds 5% to the 2,975 mL base and Moderate activity multiplies it by 1.25, giving a Recommended 3,905 mL. Minimum is 2,550 mL and Max Safe is 4,250 mL, and Optimal is capped there. His goal begins at 2,600 ml. Logging 750 ml water, 250 ml coffee and 330 ml fruit juice counts as 750 + 200 + 280.5 = 1,230.5 ml, about 47% of the goal.
When to use the water intake calculator
- Checking against the reference value. See how your weight-based target compares with 2.6 L or 2.1 L of drinks.
- Preparing for a tramp or a long ride. Raise activity and climate to see how the target grows, then log water and sports drinks along the way.
- Seeing what coffee does. Log flat whites and see how a drink counted at 0.8 changes the total.
- Following a streak. Meet the goal each day on the Progress tab to build a run of days.
What the water intake calculator does not do
- The reference values are for healthy adults and for drinks only, so water from food is not counted.
- The Health NZ guide of 8 to 10 cups is a general rule and does not take account of body size, heat or exercise.
- Pregnancy and breastfeeding add to the calculated target but not to the reference goal. A midwife or GP can say what is right for you.
- Reminders appear only while the page is open, and old days are summarised in the last seven days of bars.
- If you have heart, kidney or another condition affecting fluids, your GP's advice overrides any formula here.
When something else is a better fit
- When you want a daily check-off with real streaks and history, use the Habit Tracker.
- When you want calories and macro targets for the same profile, use the Calorie Calculator.
- When you have a medical condition that affects fluids, use your clinician's guidance, which overrides any general formula.
Questions about the water intake calculator
How much water does New Zealand guidance suggest?
The shared reference values are 2.6 L of drinks for men and 2.1 L for women. Health NZ gives a plain guide of 8 to 10 cups, or 2 to 2.5 L, of fluid a day.
Why is the target different from my goal?
The target comes from weight and your settings. The goal starts from the reference value and is yours to change. For the example man they are 3,905 ml and 2,600 ml.
Does food count?
Not in this goal. Total water including food is 3.4 L for men and 2.8 L for women, but the starting goal is for drinks alone.
Why is Optimal the same as Max Safe in the example?
Optimal would be 4,295 mL, which is above the 4,250 mL ceiling of 50 mL per kilogram for 85 kg, so the tool uses the ceiling.
Is this advice for my own health?
No. It applies general figures. Talk to your GP if you take medicines, have a long-term condition or are unsure how much fluid is right for you.