Why was the Hydration Calculator created?

Hydration scientists working with The Beverage Institute For Health & Wellness felt that consumers could benefit by better understanding their basic hydration needs and how various physical-activity factors like the type of sport, duration, intensity, and ambient (air) temperature affects hydration needs. The Hydration Calculator was created to enable consumers to obtain this information in an engaging, interactive manner.

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What is the scientific basis for the Hydration Calculator?

The U.S. Adequate Intake (AI) recommendations for water established by the Institute of Medicine (IOM) in 2004 are the basis for the Hydration Calculator estimates of basic (non-exercise related) daily hydration needs. This output reflects the amount of water, derived from food and beverages in the diet, that the IOM believes will ensure adequate hydration for most healthy inactive individuals living in moderate climates in the U.S. Those who live in hot climates may need more.

Results from the second section of the Hydration Calculator, which estimates hydration needs related to physical activity, are based on a formula developed by the BIHW in collaboration with leading U.S. sports hydration experts and draws from physical activity and hydration research. Because a great deal of published research exists in the area of hydration and sports performance, this formula includes a number of exercise-related factors that are known to impact hydration needs, including age, weight, exercise intensity and duration, as well as  ambient (air) temperature.

Although the Hydration Calculator is based on the most current scientific information available related to basic and exercise hydration needs, it provides only an approximation because hydration needs vary considerably from individual to individual. The Calculator should be used as an educational tool to better understand basic hydration needs and the overall impact of exercise on those needs, and the Beverage Institute makes no representation as to the accuracy of the results produced by the Calculator for any individual. Use of this calculator is not a substitute for actually determining fluid needs for exercise by monitoring fluid loss during exercise or the advice of an athletic trainer or healthcare professional.

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Why don’t the results for my Estimated Total Daily Hydration Needs change when I change the weight input?

Although the Hydration Calculator asks for your weight in the first screen, this information is only used to generate results in the second section of tool, which examines how factors related to physical activity affect hydration needs.  Changing the Calculator’s weight input while exploring the exercise-related hydration section will affect the results.

On the other hand, results for the first part of the tool, which estimates basic (non-exercise related) hydration needs do not change when the weight input is changed. This is because the basic or general hydration results are is based on the 2004 Adequate Intake (AI) recommendations for water developed by the U.S. Institute of Medicine (IOM) -- which varies only with age and gender. The IOM recommendations estimate the amount of water from food and beverages in the diet that will provide adequate hydration for healthy, inactive individuals living in temperate climates in the U.S. 

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Why don’t the results for the Estimated Total Daily Hydration Needs increase after age 19? I thought older adults needed more water.

Results for the first part of the tool, which estimates basic (non-exercise related) hydration needs do not change with age inputs greater than 19 because this output is based on the 2004 Adequate Intake (AI) recommendations for water developed by the U.S. Institute of Medicine (IOM). The IOM water recommendations, which estimate the amount of water from food and beverages in the diet that will provide adequate hydration for healthy, inactive individuals living in temperate climates in the U.S., differ only by gender from age 19 to 70+.

It is true, however, that dehydration is a major concern for older adults – but the issue appears more related to low fluid intake rather than increased needs. Although the body system responsible for regulating water loss via the kidneys -- and thus the ability to conserve body water -- appears to be less robust in the elderly, research suggests that healthy elderly are generally able to maintain fluid balance by responding to their thirst. However age-associated physiologic changes, including thirst impairment, incontinence, reduced mobility and confusion, can limit voluntary fluid intake, particularly among institutionalized elderly and frail older adults in the community. For these individuals, poor hydration can have significant consequences. Dehydration in the elderly is associated with increased risk of falls, urinary tract infections, dental disease, bronchopulmonary disorders, kidney stones, cancer, constipation, and impaired cognitive function.

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Why don’t the results for Exercise Hydration Needs change when the air temperature is below 59°F (15°C)?

The Hydration Calculator assumes that compensatory (warm) clothing is worn when air temperatures dip below 59°F (15°C).

Why does the calculator set a limit exercise hydration needs to 1.5 L (50 oz)?

Hydration is very important during exercise. However, there have been concerns that some who exercise might over consume fluids, which can dilute the electrolytes in the bloodstream and lead to a condition know as hyponatremia. Therefore because the Hydration Calculator is designed for educational purposes, the tool is set at a limit of 1.5 L (50 oz.) per hour for maximum recommended fluid consumption during any single exercise session as a precaution. If you exercise in strenuous conditions for a long period of time, consult your trainer or other specialized sports health professional to ensure that you have a proper and safe hydration plan in place. You may also want to learn how to calculate your own Sweat Rate.

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The results for Total Daily Hydration Needs are much greater than what I normally drink. Do I really need that much water?

Although the Hydration Calculator is based on the most current scientific information available related to basic and exercise hydration needs, it provides only an approximation because hydration needs vary considerably from individual to individual. The Calculator should be used as an educational tool that helps you better understand basic hydration needs and the overall impact of exercise on those needs. Use of this calculator is not a substitute for actually determining fluid needs for exercise by monitoring fluid loss during exercise or the advice of an athletic trainer or healthcare professional.

Also keep in mind that in addition to beverages, foods also contain water. Consuming a lot of juicy fruits, salads, yogurts, cooked cereals, rice, pastas and other foods high in water content may reduce the amount you need to drink to meet your hydration needs.

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Why is there a difference between the amount of fluid recommended under “Estimated Total Daily Hydration Needs” and the number of glasses that appear when I click on “What does this mean?”

The IOM has estimated that Americans obtain about 80% of their daily fluid needs through water and other beverages and about 20% from foods. The Calculator uses this IOM 80% figure to estimate the amount of water and other beverages you should consume each day.

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