Reference scenario: a 70 kg (154 lbs) adult male with an active routine in a temperate climate — the calculator below is prefilled with exactly these inputs. The calculator returns 3.3 L per day for a male reference input and 3.0 L for a female reference input — about 13 and 12 glasses of 250 ml. At the same weight and climate the full range runs from 2.5 L (sedentary) to 3.7 L (very active). Enter your own weight, sex, activity and climate below to replace these reference inputs with your result.
During exercise, your body prioritizes blood flow to muscles and cooling. It temporarily reduces kidney function and digestive activity. Once you stop, your body shifts into recovery mode — and this is when proper rehydration directly affects how well (and fast) you recover.
Dehydration after exercise delays muscle protein synthesis, increases muscle soreness, raises resting heart rate, and impairs glycogen replenishment. In short: if you skip post-workout hydration, you undermine the benefits of the workout itself.
Sports science has established a clear guideline: replace 150% of fluid lost during exercise. The extra 50% accounts for ongoing losses through urine production as your kidneys resume normal function. Here's how to apply it:
For example: if you lose 0.8 kg during a workout, drink 1,200 ml over the next 2–4 hours.
Don't attempt to replace all lost fluid immediately — your stomach can only absorb about 250–300 ml every 15 minutes. A practical approach:
For most workouts under 60 minutes at moderate intensity, plain water is perfectly adequate. Your next meal will naturally replace any lost electrolytes. However, in these situations, consider adding electrolytes:
You don't need expensive supplements — a pinch of sea salt in water with a squeeze of lemon provides sodium and potassium naturally.
Monitor these indicators in the hours after exercise: if your urine remains dark yellow 2 hours post-workout, you haven't replaced enough fluid. Persistent thirst, elevated resting heart rate, headache, or unusual fatigue the next day all point to inadequate recovery hydration.
Begin drinking within 15–30 minutes of finishing your workout. Drink steadily over the next 2–4 hours rather than all at once.
For workouts under 60 minutes, water is sufficient. For intense sessions over 60 minutes or in heat, a drink with electrolytes helps replace lost sodium and potassium.