Daily Water Intake Calculator — How Much Should You Drink?
Even mild dehydration cuts gym performance and increases hunger. This tool sizes your intake to bodyweight, training and hot weather.
3.8L
The formula used
35 ml per kg of bodyweight, plus 500 ml per training hour, plus 500 ml in hot weather or outdoor work. An 80 kg person training an hour in summer: 2.8 + 0.5 + 0.5 = 3.8 litres.
Signs you're not drinking enough
Dark urine is the clearest signal — it should be pale yellow. Also afternoon headaches, dizziness on standing, dry mouth and a sudden drop in training performance.
Water and fat loss
A glass before meals reduces intake, and water supports digestion and regularity on a high-protein diet. Don't rely on thirst alone — spread intake across the day.
FAQ
Is 8 glasses a day correct?▼
It's a rough old rule. Needs vary with size, activity and climate, so a per-kilo calculation is more accurate.
Do tea and coffee count?▼
Yes, they count toward fluids, but keep most of your intake plain water to limit sugar and caffeine.
Can I drink too much water?▼
It's rare but possible if you drink litres in a short window. Spread intake through the day instead.