Water Intake Calculator for Women
A daily fluid guide for women, based on the US National Academies adequate intake: about 2.2 litres a day from drinks. It adjusts for pregnancy and breastfeeding, and adds a rough allowance for exercise and hot weather.
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Daily fluid guide, from drinks
2.2 litres
About 9.2 cups (240 ml each) or 74 US fluid ounces. All drinks count, not only water.
- Adequate intake for your life stage
- 2.2 litres
- Exercise allowance (rule of thumb)
- none
- Hot weather allowance (rough)
- none
- Total water for your life stage, with food
- 2.7 litres
This is a guide, not a target. Drink when you are thirsty and aim for pale yellow urine. If you have a heart or kidney condition, or you are on a fluid restriction, follow your doctor's advice. Do not force yourself to drink much more than you need.
This is general information, not medical advice. It cannot take your own health history into account. For anything that worries you, speak to a doctor, midwife or pharmacist.
How it works
The starting point is the adequate intake set by the US National Academies (2004). For women aged 19 and over it is about 2.7 litres of total water a day from all drinks and food. About 2.2 litres of that, around 9 cups, comes from drinks. The rest comes from food. This calculator shows the drinks part.
The same report gives higher figures for two life stages. In pregnancy the drinks figure is about 2.3 litres a day (3.0 litres of total water). When breastfeeding it is about 3.1 litres a day (3.8 litres of total water).
Daily guide = life stage figure + exercise allowance + hot weather allowance. The exercise allowance is 400 ml for every 30 minutes of sweaty exercise. The hot weather allowance is 500 ml. These two are rules of thumb chosen for this tool, not published targets, because sweat loss differs a lot from person to person.
All drinks count, including tea, coffee and milk. Cups are 240 ml and fluid ounces are US fluid ounces (29.57 ml). The European Food Safety Authority uses a lower figure of 2.0 litres of total water a day for women, so treat any single number as a guide.
What it cannot tell you
- It is a population guide, not a personal target. The adequate intake is based on what healthy, well-hydrated women in the US typically drink. Your own need changes with your body size, your food, the climate and how much you sweat.
- Thirst and urine colour are the practical guide. If you are rarely thirsty and your urine is pale yellow, you are probably drinking enough.
- If you have a heart or kidney condition, or your doctor has put you on a fluid restriction, follow your doctor's advice and not this calculator.
- More is not better. Drinking far more than you need in a short time can dangerously lower the sodium level in your blood. Do not force yourself to drink past thirst to reach a number.
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Common questions
A woman needs about 2.2 litres of fluid a day from drinks, which is around 9 cups or 74 US fluid ounces. This is the US National Academies adequate intake for women, and it sits inside a total of 2.7 litres a day once the water in food is counted. Needs go up with exercise, heat, pregnancy and breastfeeding.
No, the 8 glasses of water a day rule is not based on firm evidence. It is a rough round number. The US National Academies did not set a fixed number of glasses and said most healthy people meet their needs by letting thirst guide them. All drinks and the water in food count towards your intake.
Drinking half your body weight in ounces of water is a popular rule, but it does not come from a health body or a guideline. The National Academies and EFSA figures for adults are not set by body weight. A guide based on the adequate intake, your activity and the weather is a better starting point, with thirst as the final check.
In pregnancy the US National Academies adequate intake is about 2.3 litres a day from drinks, around 10 cups. When breastfeeding it is about 3.1 litres a day from drinks, around 13 cups. Ask your midwife or doctor if you are unsure, and tell them if you cannot keep fluids down.
Yes, tea and coffee count towards your daily water intake. The US National Academies report says caffeinated drinks contribute to total water intake in the same way as other drinks. Water, milk, juice and the water in food all count too.
Sources
- US National Academies: Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005), chapter 4: Water
- US National Academies news release: report sets dietary intake levels for water, salt and potassium (2004)
- EFSA: Scientific Opinion on Dietary Reference Values for water (2010)