How to Calculate Your Water Intake During Exercise and Everyday Life

The importance of hydratation

Drinking enough water is crucial for your body, especially if you’re active. Here are four key reasons why hydration plays a vital role in muscle recovery:

Why hydration matters more than people think

Water regulates temperature, supports muscle function, helps transport nutrients and maintains mental clarity. Even a small drop in hydration level (1–2% of body weight) can reduce performance and increase fatigue.

In hot and humid environments — like Southeast Asia — these effects are amplified.

Daily water requirements: a simple formula

The baseline formula

Most adults need 30–35 ml of water per kg of body weight per day.

Example for 70 kg → 2.1 to 2.4 litres/day.

Adjusting for climate and lifestyle

Add +10–20% if :

• you live in a hot climate

• you have an active job

• you sweat easily

• your sleep is poor

• you consume caffeine regularly

Hydration is not just about drinking more — it’s about matching your needs to your environment.

How to calculate hydration needs during exercise

Before exercise

Drink 5–7 ml/kg about 3 hours before activity.

During exercise

Aim for 150–250 ml every 15–20 minutes depending on temperature and intensity.

If you sweat heavily, increase the frequency.

After exercise

Rehydrate based on weight lost through sweat.

Formula:

Weight lost (kg) × 1.5 = water to drink (litres)

The practical 3-step hydration test

Weigh yourself before training

Minimal clothing, no shoes.

Weigh yourself after

The difference = sweat loss (1 kg = 1 litre of water).

Rehydrate properly

Example:

0.8 kg lost → drink 1.2 L in the following 2 hours.

This prevents cramps, fatigue, headaches, and post-training drop in energy.

Conclusion

Hydration is one of the simplest tools to improve performance and recovery. Whether you’re training casually or living in a tropical climate, applying these formulas helps your body work at its best — daily and during exercise.

References:

1. Sawka MN, Cheuvront SN, Carter R. “Human Water Needs.” Journal of Applied Physiology. 2005. Link to PubMed

2. Bergeron MF. “Hydration and Cramps.” Sports Medicine. 2008. Link to PubMed

3. Casa DJ, Armstrong LE, Hillman SK. “Fluid Replacement and Heat Stress.” Journal of Athletic Training. 2000. Link to PubMed

4. Griffin LY. “Hydration and Joint Health.” Journal of Orthopaedic Research. 2009. Link to PubMed