How much water do you actually need? Enter your weight, activity and climate — the calculator uses the common 30–35 ml/kg baseline with exercise and heat adjustments, and translates the result into real-world bottle refills.
Baseline: 33 ml per kg of body weight (the midpoint of the widely used 30–35 ml/kg range) · Exercise: +350 ml per 30 minutes · Hot climate: +500–750 ml. Around 20% of daily fluids typically arrive via food, and normal coffee and tea count toward the total — so the number here is a target for all fluids, not plain water heroics.
Not medical advice: fluid needs vary with health conditions, pregnancy and medications — kidney or heart patients especially should follow their doctor's guidance, not a calculator.
The habit research is boring and consistent: people drink what's in front of them. A bottle sized to your target — one fill, or two, and done — beats willpower every time.
The 'drink your water' bottle that never leaves the algorithm — time markers guilt you through the day, straw included.
🚚 Free shipping on most orders · price at time of writing
The Stanley-style tumbler at a fraction of the price — keeps ice for 24h, fits cup holders, comes in every pastel.
🚚 Free shipping on most orders · price at time of writing
