Sports Hydration — Calculating Water Needs During Exercise

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Overview

Even mild dehydration of 2% body weight impairs athletic performance by 10-20%. Calculating your fluid needs before, during, and after exercise protects both performance and health.

The Formula

Pre-exercise: 500ml 2hrs before | During: 150-250ml every 15-20min | Post: 1.5L per kg lost

Standard formula used by professionals worldwide

Worked Example

Step-by-step

70kg runner racing 1hr: sweat ~1L/hr → drink 150ml every 15min during race → 600ml

Key Points

Accuracy: Results are as accurate as the inputs you provide
Units: Always use consistent units throughout your calculation
Privacy: All calculations on CalcHub Pro run in your browser — nothing is sent to any server

Frequently Asked Questions

Should I drink sports drinks or water?

Water for under 60 minutes. Electrolyte drinks for longer or hot conditions.

How do I measure my sweat rate?

Weigh before and after 1-hour training. Each kg lost = approximately 1 litre of sweat.

Signs of over-hydration?

Nausea, headache, confusion from low blood sodium (hyponatremia). Rare but serious.

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