Water Intake Guide

Why hydration matters

Water supports energy levels, digestion, temperature regulation, and cognitive performance. Dehydration can reduce physical performance and concentration. This guide explains how to estimate daily intake.

Baseline intake

Many guidelines start with a weight-based estimate. A common baseline is 30 to 35 ml per kg of body weight per day. That produces a starting point you can adjust.

Activity and climate adjustments

Exercise and hot climates increase fluid needs. For moderate exercise, add 0.5 to 1 liter per day. For intense activity or hot weather, increase further.

Worked example

A 70 kg adult at moderate activity might target 2.3 to 2.7 liters daily. If exercising in hot weather, add another 0.5 to 1 liter.

Signs of dehydration

• Dark urine
• Headaches or dizziness
• Low energy
• Dry mouth

Hydration from food

Some water comes from food, especially fruits and vegetables. About 20-30% of daily intake can come from food. Use that as context, but still aim for sufficient fluids.

Recommended calculators

• Water Intake Calculator
• Calorie Calculator

References

• Institute of Medicine hydration guidance
• Public health resources on water intake