Water intake calculator.

The general adult reference is 2.0 litres for women or 2.5 litres for men each day, including water in food and all drinks. Exercise and heat change the guidance, not the calculated litres. This is not extra water to drink or a personalised prescription.

This weight-based guide uses 30–35 mL/kg/day from NICE adult nutrition-support guidance. It includes fluid from food and all drinks. It is not a validated personalised hydration target for every healthy adult or every body size.

The tool does not add automatic litres for exercise, heat, sauna or GLP-1 use. A high estimate is not a guarantee of a safe daily intake.

Food, milk and other drinks contribute to total fluid. This number is not an extra volume of water to drink.

Heat and activity can change your needs. Drink regularly; do not force large amounts of water quickly.

Persistent vomiting, inability to keep fluids down, dizziness or very little urine need medical advice, not a higher calculator target.

Before you use this calculator

These tools offer general information for adults. Results are estimates, not a diagnosis, treatment plan or prescription. Your clinician can help you decide what fits your health, medicines and goals.

For adults 18+ who are not pregnant or breastfeeding. Do not use this estimate if you have a fluid restriction, heart or kidney disease, significant illness, or ongoing vomiting or diarrhoea. Get advice specific to you.

Your calculation happens in this browser. Do not enter your name or medical records. These tools do not assess medicine suitability or dosing.

Tests or treatment are recommended only when clinically appropriate. Laboratory charges are separate.

Sources and context

• MHRA: GLP-1 medicines - what you need to know

  Safety information, pregnancy, contraception, surgery and variability between products. UK authorisations are not South African authorisations.

• EFSA: Dietary reference values for nutrient intakes

  Adult total water reference and carbohydrate/fat ranges. Total water includes food and drinks; published 2010.

• NICE CG32: Nutrition support for adults - recommendations

  30–35 mL/kg/day fluid as nutrition-support guidance in selected adults, not a universal wellness hydration formula. Also identifies unintentional loss and inadequate intake as clinical concerns.

Sources checked in the supplied release pack on 18 October 2026. Clinical review by Dr Addinall and compliance review by Thomas are complete.