Water intake calculator
Pick female or male and, if it applies, pregnancy or breastfeeding. You get the daily water intake that European and US reference values give, and how much of it usually comes from drinks. Weigh yourself before and after a session to see how much to drink afterwards.
What the numbers mean
Both figures are total water a day, from drinks of every kind and from the water in food:
| European Food Safety Authority | US National Academies | |
|---|---|---|
| Women | 2.0 L | 2.7 L |
| Men | 2.5 L | 3.7 L |
| Pregnancy | 2.3 L | 3.0 L |
| Breastfeeding | 2.7 L | 3.8 L |
They are adequate intakes, set from the amounts healthy people take in. The US National Academies say theirs is not a requirement to hit each day. Thirst and the drinks people have at meals keep most people’s water at normal levels, and activity and heat raise what you need.
After a session
How much people sweat varies a lot. Dietitians of Canada, the Academy of Nutrition and Dietetics and the American College of Sports Medicine say that 1 kg of weight lost during exercise is about 1 L of sweat, and suggest drinking 1.25 to 1.5 L for every 1 kg lost, after the session. Drinking more than you sweat can lower the sodium in your blood, so the aim is to replace what was lost.
How it is worked out
The daily figure is the European Food Safety Authority’s value for your sex, pregnancy or breastfeeding, with the US figure beside it. In the US National Academies’ data, about 80% of water came from drinks, so the drinks figure is 80% of the daily figure, to one decimal. For a woman: 2.0 L a day, about 1.6 L from drinks.
After a session: (weight before − weight after) in kg × 1.25 to × 1.5 litres. From 70.0 kg to 69.2 kg, 0.8 kg was lost: 0.8 × 1.25 = 1.0 L to 0.8 × 1.5 = 1.2 L.
With weights in pounds, litres are also shown in US fluid ounces, at 33.8 fl oz to a litre.
In Nume: a drink you have most days, like a morning coffee, can log itself at its time. Before a timed session, Nume puts a note in Talk about what to eat beforehand.
Ask an assistant
ChatGPT, Claude, Gemini, Perplexity and other assistants can run this calculator from a link and read the answer as text. Ask one to open this link with your own numbers:
https://nume.co.in/tools/water-intake-calculator/answer?sex=female&before_kg=65&after_kg=64.4
stage can be pregnant or breastfeeding. The weights before and after a session are optional. The link on its own lists every input.
Apps that take an MCP server, such as Claude and Cursor, can add all four calculators at once: see Tools.
Checked on · The Nume team
Sources
- European Food Safety Authority: Summary of Dietary Reference Values, version 4 (2017)
- National Academies: Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005), summary
- Dietitians of Canada, Academy of Nutrition and Dietetics and American College of Sports Medicine: Nutrition and Athletic Performance (2016)