Hydration targets vary by body, climate and activity. The ChrysoKit Water Intake Calculator gives you a personalised daily estimate from a handful of inputs, in metric or imperial.
Why use it
"Drink eight glasses" is a one-size-fits-all rule that ignores everything specific to you. Five inputs gives a usable, personalised number.
How to use the Water Intake Calculator
- Pick metric or imperial units.
- Enter your age, biological sex, weight and height.
- Pick an activity level (sedentary to very active).
- Pick a climate (temperate, hot, cold or humid).
- Read the suggested daily intake.
Features worth knowing
Personalised estimate
The formula combines age, sex, body weight, height, activity and climate, rather than a single rule of thumb.
Metric and imperial
kg/cm or lbs/in, ml or fl oz. Pick the one your scale and your water bottle already use.
Practical guidance
The result is shown both as total fluid and as a number of common glass sizes, so it translates to "drinks per day" not just "ml".
Pro tips
- Coffee, tea and food all count toward total daily fluid intake. Pure water is not the only contributor.
- Thirst is a late signal. If you only drink when thirsty, you are usually already a bit behind.
- Hot weather and intense exercise can push intake well above the baseline. Adjust upward on those days.
Privacy first. The Water Intake Calculator runs entirely in your browser. Nothing you enter is uploaded.
This is a guideline, not medical advice. If you have specific health conditions, defer to a clinician for your real target.
Open the tool: Water Intake Calculator →
A heatwave week in a Mediterranean summer: hydration in practice
Forty-degree afternoons change the hydration problem from theoretical to operational. During a Greek July heatwave, the textbook numbers stop being abstract: sweat losses outdoors can reach a litre per hour, thirst lags behind need, and the populations at real risk... older adults whose thirst signal has dulled, outdoor workers, anyone on diuretic medication... can slide toward trouble while feeling merely tired.
What practitioners actually recommend for such weeks, beyond "drink more": front-load the morning, because starting the day's heat already hydrated beats chasing losses at 15:00. Pair water with food and electrolytes during heavy sweating... plain water in large volumes during all-day heat exposure dilutes sodium, and the watermelon-feta habit of Greek summers is accidental electrolyte engineering. Use urine colour as the dashboard, checked at midday rather than morning. And treat alcohol's effect honestly: the evening beer is a diuretic arriving exactly when the day's deficit peaks.
The week-long pattern matters more than any single day: cumulative mild dehydration across a heatwave presents as headaches, poor sleep and irritability that nobody attributes to water. A calculated daily target, adjusted upward for the heat, turns the week into a checklist instead of a slow-motion deficit... unglamorous, and exactly what August requires.