How this calculator works
IOM adequate intakes provide adult baselines of 3.7 L/day for males and 2.7 L/day for females, including food moisture and every beverage. About one fifth often comes from food. We add an assumed 0.35 L per 30 minutes of exercise; this add-on is not an IOM recommendation and becomes especially uncertain during prolonged exercise. This is not for pregnancy, lactation, kidney disease, heart failure or prescribed fluid restriction. The result is an estimate for information only and is not medical advice.
Formula
Total water (L/day) = baseline + 0.35 x exercise minutes / 30.
Worked example
A male baseline plus 30 minutes of exercise gives 3.7 + 0.35 = 4.05 L/day total water. A sedentary female baseline is 2.70 L/day.
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Frequently asked questions
Is this all water I should drink?
No. The estimate includes food moisture and all beverages, so it is not a plain drinking-water target.
Does it account for heat or sweat rate?
No. Climate, sweat losses and individual conditions can change needs substantially.
What if I exercise for less than 30 minutes?
The add-on is proportional: 0.35 L per 30 minutes, so 15 minutes adds 0.175 L.