EVERYDAY TOOLS
Adult hydration estimator
An educational illustration of the original CalcYourInvest weight-based heuristic. It is not an individually validated fluid prescription or a clinical recommendation.
Your assumptions
Range: 20–500
Results update as you change your assumptions.
Legacy heuristic estimate
An unvalidated legacy heuristic for adults, not a clinical recommendation. Children’s mode has been retired.
BEHIND THE CALCULATION
Understand your result.
Explore the assumptions behind a simple adult hydration estimate based on body weight and daily conditions.
How the calculation works
The legacy model starts with weight in kilograms × 0.033 litres, then multiplies by 1.05 for male or 0.95 for female, and by 0.9 for the senior option. Activity adds 0, 0.3 or 0.6 litres; climate adds −0.2, 0 or 0.4 litres for cold, moderate or hot conditions. These experimental coefficients are not clinically validated and are not an EFSA formula.
For 70 kg, the unadjusted weight-based calculation is 70 × 0.033 = 2.31 litres. Your selected model options can change that number; individual fluid needs may differ.
Assumptions & limitations
- For adult educational use only. The estimate is not suitable for children or individual clinical planning.
- The weight-based model is a heuristic, not a validated medical standard.
- Water also comes from food and other drinks; the output is not an instruction to drink that volume of plain water.
- Individual needs vary. Follow professional guidance if you have fluid restrictions, relevant health conditions, are pregnant or breastfeeding.