What this tool does
Create a simple daily fluid-planning range from body weight and exercise minutes, with the result shown in litres.
How to use it
- Enter body weight in kilograms.
- Add the number of active exercise minutes expected that day, from 0 to 1,440.
- Calculate the low and high planning values, then adjust sensibly for food, other drinks, climate and health guidance.
Formula and method
The calculator uses a planning heuristic, not an official CDC formula: low = weight×0.030 L + exercise minutes÷30×0.35 L; high = weight×0.035 L + the same exercise allowance. The exercise allowance adds 0.35 L for each 30 minutes entered.
Worked example
At 70 kg with 30 minutes of exercise, the base range is 2.10–2.45 L and the exercise allowance is 0.35 L. The displayed planning range is therefore 2.45–2.80 L.
Common uses
- Setting a practical bottle-refill target
- Comparing rest and exercise-day estimates
- Starting a hydration discussion with a clinician or coach
Limitations
This is a broad planning estimate and counts fluid, not only plain water. Actual needs vary with age, sex, pregnancy or breastfeeding, food moisture, heat, altitude, illness, medicines and kidney or heart conditions. More is not always safer; follow individual medical advice and seek help for dehydration or fluid-restriction concerns.
FAQ
Is this the CDC daily-water formula?
No. CDC explains that needs vary and that food and beverages both contribute; the weight-and-exercise equation is this calculator’s transparent planning heuristic.
Should every displayed litre be plain water?
Not necessarily. Fluids can come from water, other beverages and foods, although plain water is a useful calorie-free choice.