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Hydration Calculator

💧Hydration Calculator

What is Hydration Calculator?

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Daily water requirements vary based on body weight, physical activity, and climate. The European Food Safety Authority (EFSA) recommends 2.0 litres/day for adult women and 2.5 litres/day for adult men from all sources (food and drink). The 35 ml/kg baseline accounts for roughly 60% of these requirements from beverages.

Calkulon makes complex calculations simple — built for students and everyday problem-solvers.

How to Hydration Calculator

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  1. 1Base: 35 ml per kg body weight per day
  2. 2Activity bonus: +350 ml (moderate exercise) to +700 ml (intense exercise)
  3. 3Climate bonus: +200 ml (warm) to +500 ml (hot/humid)
  4. 4All fluid counts: water, milk, juice, tea, coffee (moderate)

Worked Examples

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Example 1
Given:70 kg, moderate activity, warm climate
Result:2,800 ml/day (≈ 11.8 cups)

2,450 base + 350 activity

Real-World Applications

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Tracking personal health and fitness goals

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Guidance for healthcare conversations with your doctor

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Monitoring progress during a weight management programme

Frequently Asked Questions

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Q

What is Hydration?

A

Daily water requirements vary based on body weight, physical activity, and climate. The European Food Safety Authority (EFSA) recommends 2

Q

How accurate is the Hydration calculator?

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The calculator uses the standard published formula for hydration. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

Q

What units does the Hydration calculator use?

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This calculator works with kilograms, inches, litres, percentages. You can enter values in the units shown — the calculator handles all conversions internally.

Q

What formula does the Hydration calculator use?

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The calculator applies the standard formula for this type of calculation. See the 'How It Works' steps above for the detailed formula breakdown.

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Pro Tip

A quick hydration check: urine should be pale straw yellow. Dark yellow or amber indicates dehydration. Clear urine may indicate overhydration. Thirst is already a sign of mild dehydration (1–2% body weight fluid loss).

For informational purposes only. This tool is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional.
Formula-verified for precision
Reviewed October 2026
Our methodology

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