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Water intake calculator.
Roughly how much water to aim for in a day, from your weight and how much you sweat. It is a starting point, not a prescription: your thirst is better at this than any formula.
How this is worked out, and what it misses
The sum. 35 ml per kilogram of bodyweight, plus about 500 ml for each hour of hard training. At 80 kg with an hour in the gym, that is roughly 3.3 litres. It is the same figure the Whey to Go app sets your water goal from.
Food counts, and this figure does not include it. Somewhere around a fifth of the water most people take in comes from what they eat, and more if you get through a lot of fruit, vegetables or soup. So the number above is total water, not glasses you have to drink on top of your meals.
Thirst beats arithmetic. Barring a medical reason not to trust it, thirst is a better guide than any per-kilo rule, and pale straw-coloured urine is the check that actually works. Heat, altitude, illness, caffeine, alcohol and pregnancy all move the number, and none of them are in this sum.
More is not better. Drinking far beyond thirst dilutes blood sodium, and in rare cases that is dangerous rather than merely inconvenient. If you are forcing litres down to hit a target, the target is wrong.
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This is an estimate and a starting point, not medical advice. Every equation of this kind is a population average, so your real burn can sit a few hundred kcal either side of it. Track for two or three weeks and adjust to what actually happens on the scales. If you are pregnant, managing a health condition or unsure, speak to a doctor or dietitian first.
There is no account here and no tracking cookie, so nothing you enter is saved to a profile or tied to you. The sums run on our server, and your answers travel in the page address, which is what makes a result shareable. Treat a link you send as carrying those numbers with it.
Now log against it
A number is only useful if you can hit it. Whey to Go tracks food and training against targets like these, on your device, with no account and nothing sold.