VoltraHow much water do you need a day?
The European Food Safety Authority puts an adequate intake of water at 2.0 litres a day for women and 2.5 litres for men, counting water from food as well as drinks, for moderate temperatures and activity [1]. About a fifth usually comes from food [1], which leaves about 1.6 and 2.0 litres to drink (calculated).
In hot weather, the WHO advises drinking a cup of water an hour and at least 2 to 3 litres a day [2].
By your weight: the Saudi health ministry's formula
Saudi Arabia's health ministry has an adult water calculator that multiplies your weight by 35 ml per kilo if you are 20 to 55, 30 ml from 56 to 75, and 25 ml over 75; it doesn't calculate for anyone under 20 [5]. It says all drinks count towards this, that pregnant and breastfeeding women, athletes and people who work in the heat may need more, and that people with kidney failure and some heart patients need less, as their doctor advises [5].
| Weight | Age 20 to 55 | 56 to 75 | Over 75 |
|---|---|---|---|
| 60 kg | 2.10 L | 1.80 L | 1.50 L |
| 70 kg | 2.45 L | 2.10 L | 1.75 L |
| 80 kg | 2.80 L | 2.40 L | 2.00 L |
| 90 kg | 3.15 L | 2.70 L | 2.25 L |
| 100 kg | 3.50 L | 3.00 L | 2.50 L |
| 110 kg | 3.85 L | 3.30 L | 2.75 L |
Calculated from the ministry's formula: weight × 35, 30 or 25 ml [5].
The ministry doesn't say whether its figure includes water from food. EFSA's figures are total water, about a fifth of which usually comes from food [1]. So at 70 kg the ministry gives 2.45 litres of fluids, against about 2 litres to drink for men in EFSA's figures (calculated). The gap is small, and heat and exercise raise both.
Why the Gulf is different
The 2.0 and 2.5 litre figures only apply to moderate temperatures and activity [1]. In extreme heat and hard exercise, water losses can reach about 8 litres a day, and have to be replaced [1]. That is why the WHO's heat advice [2] and Saudi Arabia's health ministry, which says everyone should drink at least 2 litres of water a day and athletes need more [3], sit above the European figures.
When you train
Drink before, during and after exercise, especially in hot weather, to avoid dehydration [3].
In Ramadan
The WHO's regional office for the Eastern Mediterranean advises drinking plenty of water, at least 10 glasses, and eating hydrating foods such as soup, watermelon and green salad [4]; in Ramadan, that means between iftar and suhoor. It doesn't give a glass size, so we don't convert it to litres.
Tracking it in Voltra
Log water on the Eat tab. You set the water goal yourself on the water screen, in 250 ml steps, starting at 2 litres; the app doesn't work it out from your weight, so you can enter the ministry's number. You can also turn on hydration reminders in your notification settings.
Frequently asked
How much water do I need for my weight?
Saudi Arabia's health ministry calculator gives 35 ml per kilo if you are 20 to 55: 2.45 litres at 70 kg, 2.8 at 80 kg and 3.15 at 90 kg. From 56 the figure is lower.
Does the health ministry's water calculator include water from food?
It doesn't say. It says all drinks count. EFSA's figures are total water including food, about a fifth of which usually comes from food.
Do tea, coffee and other drinks count towards my water?
In the European Food Safety Authority's figures, yes: total water includes drinking water, beverages of all kinds and the water in food.
How many glasses is 2 litres?
It depends on the glass, which none of these sources sizes, so it's clearer to count in litres.
How much water do I need in the Gulf summer?
More than the 2 to 2.5 litres set for moderate conditions. In hot weather, the WHO advises a cup an hour and at least 2 to 3 litres a day, and more if you sweat a lot.
Sources
- EFSA Panel on Dietetic Products, Nutrition, and Allergies (2010). Scientific Opinion on Dietary reference values for water. EFSA Journal 8(3):1459. Abstract p. 1; food share p. 20; extreme conditions p. 3.
- World Health Organization. Climate change, heat and health (fact sheet). “Keep your body cool and hydrated”.
- وزارة الصحة، المملكة العربية السعودية. ترطيب الجسم والرياضة. In Arabic.
- منظمة الصحة العالمية، المكتب الإقليمي لشرق المتوسط. حافظ على صحتك في رمضان. In Arabic.
- Ministry of Health, Saudi Arabia. حساب احتياج البالغين للماء (adult water needs calculator). In Arabic. The formula is from the calculator itself, the notes from below it. Read 6 October 2026.
Sources checked on 30 September 2026.
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