Can you drink too much water?

Yes. Drinking very large amounts quickly can dilute blood sodium (hyponatremia). It's rare but serious. Use the upper practical target as a sanity check, and rely on thirst and urine color. If you have kidney/heart conditions or take diuretics, ask a clinician.

How do I estimate sweat rate?

Weigh yourself before and after a typical workout (same clothes). Sweat loss (oz) ~= (pre - post weight in lb) * 16 + fluids (oz) - urine (oz). Divide by workout hours for oz/hr. Repeat a few sessions and average.

Does coffee count toward hydration?

For most people, coffee still counts toward total fluids. If caffeine upsets your stomach or makes you urinate more than usual, count it partially and use thirst and urine color as your check.

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Hydration Calculator For Training

Use this water intake calculator to estimate daily hydration needs based on your body weight, training time, and temperature (cool, normal, or hot). Add a sweat rate (optional) for a more personalized hydration calculator for workouts. You'll get a minimum target and an upper practical range, so the result stays realistic. Start with US units (lb/oz) and switch to metric (kg/L) anytime. Estimates only; not medical advice. See Methods & assumptions.

Methods & assumptions

This variant focuses on Hydration Calculator For Training.

This hydration calculator uses a baseline plus a training add-on, then adjusts the training add-on for temperature.

Baseline:Imperial 0.5 oz per lb. Metric 35 ml per kg.
Training add-on:If sweat rate is provided, add sweat_rate * training_hours. Otherwise, add 12 oz per 30 minutes.
Temperature multipliers (training add-on):Cool 0.8, Normal 1.0, Hot 1.2.
Minimum target:baseline + adjusted training add-on.
Upper practical target:minimum * 1.2.
Rounding:ounces to whole numbers; liters to one decimal.