Water Intake Calculator
Find your personalised daily water recommendation based on your body weight, activity level, and climate. In litres, cups, and bottles.
Daily Water Intake Calculator
How Much Water Should You Drink Per Day in 2026?
The old "8 glasses a day" rule is a rough guide at best. Your actual water needs depend on your body weight, how active you are, the climate you live in, and your overall health. This free water intake calculator gives you a personalised recommendation based on the most widely accepted formula: 33ml per kg of body weight, adjusted for activity and climate.
The Science Behind the Calculation
The European Food Safety Authority (EFSA) recommends 2.0 litres per day for women and 2.5 litres for men as a general baseline. However, the National Academies of Sciences suggests total water intake (from all sources) of 3.7L for men and 2.7L for women. Active individuals in hot climates may need 4–6 litres or more to stay hydrated during intense exercise.
Signs of Dehydration
Even mild dehydration (1–2% of body weight) impairs concentration, mood, and physical performance. Dark yellow urine, headaches, fatigue, and dry mouth are early signs. The simplest guide: your urine should be pale yellow throughout the day — clear means over-hydrated, dark amber means under-hydrated.
Does Coffee Count?
Yes — despite the mild diuretic effect of caffeine, moderate coffee and tea consumption still contributes positively to daily fluid intake. The net hydration effect of a cup of coffee is still positive. However, alcohol is dehydrating and should not be counted toward your daily water goal.
Tips to Hit Your Water Goal
Keep a 1-litre bottle on your desk and refill it twice. Drink a glass first thing in the morning before coffee. Set hourly reminders on your phone. Eat water-rich foods like cucumbers, watermelon, and leafy greens. Add lemon or mint to make plain water more appealing.