Hydration Calculator for Athletes
Your personalized daily water target for training days and competition, with sweat-rate calibration and electrolyte timing.
Athletic hydration is a two-layer problem: the daily baseline you recover between sessions on, and the session-specific replacement layered on top. This calculator nails the baseline using your weight, sex, and training volume; the session layer you calibrate yourself with pre/post weigh-ins. Sweat sodium varies up to fourfold between individuals — if you cramp in long events or see white streaks on dark clothing after workouts, you likely sweat salty and should prioritize electrolytes rather than plain water. On double-session days, rehydrate at roughly 150% of fluid lost to return to baseline before the next start.
- Baseline from weight, sex, and training load — then layer session losses
- Calibrate sweat rate: weigh before/after hard sessions (1 kg ≈ 1 L)
- Salty sweaters: cramps + white residue mean prioritize electrolytes
- Double-session days need 150% of losses replaced before restarting
Prefilled for this goal — adjust anything to match you.
Hydration Calculator for Athletes — FAQ
How much should athletes drink per hour of training?
Typical range is 400-800 ml per hour depending on sweat rate, heat, and intensity. Elite marathoners in cool conditions may need under 400 ml/h; big athletes doing two-a-days in heat can exceed a litre. Your own weigh-in data beats every rule of thumb.
Do I need electrolytes or is water enough?
Under about 90 minutes, water plus normal meals covers it. Beyond that, or in heat where you are sweating heavily, add sodium — through sports drink, tabs, or salty food. The saltier your sweat (cramping, white streaks on clothing), the more deliberate you should be.