Hydration Calculator

How much water should I drink while exercising?

General guidance is 500–1,000 ml per hour for moderate exercise in mild conditions, but actual needs depend on body weight, intensity, and heat. Use this calculator to get a personalised estimate. A practical rule: drink to thirst and check urine colour — pale yellow means well-hydrated.

What are the signs of dehydration during exercise?

Early signs include thirst, darker urine, reduced performance, and increased perceived effort. Moderate dehydration causes headaches, dizziness, and muscle cramps. Severe dehydration (>3% body weight loss) significantly impairs both cognitive and physical performance and can become dangerous.

Should I drink sports drinks or water?

For sessions under 60–75 minutes at easy to moderate intensity, water is sufficient. For longer or harder sessions — especially in heat — sports drinks that contain 30–60g of carbohydrates per litre plus sodium (500–700 mg/L) help maintain performance and replace electrolytes lost in sweat.

How do I know if I'm well hydrated?

The simplest method is urine colour: pale straw yellow indicates good hydration; dark yellow or amber suggests dehydration. You can also weigh yourself before and after exercise — every 1 kg of weight lost equals roughly 1 litre of fluid that needs to be replaced.

Does individual sweat rate matter?

Yes, significantly. Sweat rates vary from 0.5 to 2.5+ litres per hour depending on genetics, fitness, heat acclimatisation, and conditions. Athletes who sweat heavily or have salty sweat (white residue on skin/kit) should pay particular attention to sodium replacement during long events.