Water Intake Calculator
Estimate how much water to drink each day based on body weight and exercise.
Your result
Updates as you type. Based on 2025/26 UK figures where relevant.
How this is worked out
A common guide is about 33ml per kg of body weight, plus around 350ml for every 30 minutes of exercise. The NHS suggests 6–8 glasses of fluid a day.
Tips
- The NHS uses BMI as a screening tool, but waist measurement also matters.
- Estimates like BMR and body fat can vary by 5–10% from lab measurements.
- Track trends over weeks rather than day-to-day changes.
Guides for this calculator
- How to Calculate Daily Water Intake in the UK: Step-by-Step Guide
- Daily Water Intake: Common Mistakes, Tips and FAQs
More health and fitness calculators
Frequently asked questions
How does the water Intake Calculator work?
A common guide is about 33ml per kg of body weight, plus around 350ml for every 30 minutes of exercise. The NHS suggests 6–8 glasses of fluid a day.
Is this medical advice?
No. These tools give general estimates. For medical advice, speak to your GP, pharmacist or NHS 111.
Can I use these for children?
No. Children's BMI and health measures use age- and sex-specific charts. Use the NHS healthy weight calculator for children.
Why use stone and pounds?
Many people in the UK still think in stone and pounds, so we accept those units and show metric too.
This calculator gives an estimate for general information. It isn't financial, tax, legal or medical advice. Check official figures on GOV.UK or NHS.uk, or speak to a qualified adviser.