Does coffee dehydrate me?

Regular caffeine consumers retain fluid from coffee essentially normally; the mild diuretic effect adapts within days. It counts toward your total.

Can I drink too much water?

Rarely but seriously; extreme intake can dilute blood sodium (hyponatraemia). Drink to thirst plus reasonable planning, never gallons on a dare.

Do electrolyte drinks beat plain water?

For sessions beyond ~90 minutes or heavy-sweat heat exposure, yes; otherwise water and normal meals cover electrolytes amply.

Health

Water Intake Calculator

What this does

Estimate daily fluid needs from body weight plus exercise minutes, using a 33 ml/kg baseline with additions for training sweat loss.

Enter your details

Runs in your browser

How to use it

Using the water intake calculator

01
Enter your weight
Kilograms; the baseline scales linearly with body mass.
02
Add daily exercise minutes
Use your weekly average per day; count anything sweaty enough to notice.
03
Drink steadily, not all at once
Spread the total across the day; urine running pale straw indicates you are on track.

Good to know

You are probably hydrated already

For healthy people thirst is a remarkably reliable regulator. The eight-glasses folklore lacks scientific footing; beverages, soups, fruit and vegetables all contribute meaningfully to the same total-water budget.

When needs genuinely spike

Heat waves, altitude, vomiting or diarrhoea, high-protein or high-fibre diets, and long endurance sessions each push requirements well above the baseline; sometimes by a litre or more per day.

Signs worth watching

Pale-straw urine colour signals adequate hydration.
Dark urine, headache and fatigue suggest drinking more.
Clear-as-water urine all day may mean overdrinking.

How it's calculated

The math behind this calculator

Litres/day ≈ (33 ml × kg + 350 ml × (exercise minutes ÷ 30)) ÷ 1000

Baseline fluid turnover scales roughly with metabolically active mass, so we start from about 33 ml per kilogram of body weight; sitting inside the 30–35 ml/kg band used in sports-nutrition practice and compatible with National Academies adequate-intake figures for average adults.

Every half hour of exercise adds roughly 350 ml to replace sweat, then the total converts to litres for easy bottle counting.

Assumptions & limitations

Temperate climate; hot conditions raise needs substantially.
Total water includes fluid from food (~20% of intake).
Illness, pregnancy and breastfeeding alter requirements; this tool does not model them.

Worked example

A 70 kg person doing 30 minutes of daily exercise needs roughly 2.66 L; 2.31 L from the weight baseline plus 350 ml for the workout.

FAQ

Frequently asked questions

Does coffee dehydrate me?: Regular caffeine consumers retain fluid from coffee essentially normally; the mild diuretic effect adapts within days. It counts toward your total.
Can I drink too much water?: Rarely but seriously; extreme intake can dilute blood sodium (hyponatraemia). Drink to thirst plus reasonable planning, never gallons on a dare.
Do electrolyte drinks beat plain water?: For sessions beyond ~90 minutes or heavy-sweat heat exposure, yes; otherwise water and normal meals cover electrolytes amply.

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