Free hydration calculators
Know exactly how much to drink, and when.
Free calculators and plain-English guides for water, sweat and electrolytes, built for runners, gym-goers, hikers, outdoor workers and pregnant or breastfeeding moms.
Calculators
Water Intake Calculator
Use our free water intake calculator to get a personalized daily hydration goal based on your weight, activity level, and climate. Takes 30 seconds.
CalculatorSweat Rate Calculator
Calculate your personal sweat rate in liters per hour with a simple before-and-after weigh-in. Know exactly how much to drink during and after exercise.
CalculatorPost-Workout Hydration Calculator
Find out exactly how much water to drink after your workout. Enter your activity, duration, and conditions to get a personalized rehydration target in seconds.
CalculatorDaily Electrolyte Calculator
Find your daily sodium, potassium, magnesium, and chloride targets based on sex, activity level, and sweat. Free calculator, plain-English results.
CalculatorPregnancy Water Intake Calculator
Find out how much water to drink during pregnancy. Our free calculator uses National Academies guidelines and adjusts for exercise and heat.
CalculatorBreastfeeding Water Intake Calculator
Find your daily water goal while breastfeeding. Based on National Academies guidelines (~3.8 L total, ~3.1 L drinks). Free, fast, plain-English.
CalculatorHeat Index & Hydration Calculator
Find your heat index and get a plain-English hourly fluid target for your activity level. Based on NOAA's formula and CDC/NIOSH hydration guidelines.
CalculatorHiking Water Calculator
Find out exactly how much water to bring hiking. Enter your trip length, pace, and weather to get a personalized estimate in liters and pounds.
CalculatorDoes Coffee Dehydrate You? Caffeine Calculator
Find out if your daily coffee is dehydrating you. Enter your drinks below — our caffeine calculator does the math in seconds.
CalculatorElectrolytes for Running: Sodium Calculator
Find out how much sodium you need per hour on long runs, half marathons, marathons & ultras. Free calculator + plain-English guide.
Guides
How to Stay Hydrated: The Complete Guide
Learn daily water needs, signs of dehydration, food water, exercise timing and heat tips—all in one plain-English hydration guide.
Electrolytes for Hydration: When You Need Them
Learn what sodium, potassium, magnesium and chloride do, who needs extra, and the best food sources. Plain-English guide backed by trusted health sources.
Urine Color Chart: What Your Pee Says About Hydration
Use our 8-shade urine color chart to read your hydration level in seconds. Learn what each shade means, what throws it off, and when to call a doctor.
Electrolyte Drinks Compared: Liquid IV, DripDrop, LMNT, Pedialyte & More
Compare sodium, potassium and sugar in Liquid IV, DripDrop, LMNT, Pedialyte and others. Find the best electrolyte drink for your activity and needs.
Homemade Electrolyte Drink (and Does Himalayan Salt Help?)
Make a simple DIY electrolyte drink with salt, citrus, and honey. Plus the honest truth about Himalayan salt and hydration—backed by real sources.
Hydration Vests & Bladders: How to Choose
Pick the right hydration vest, pack, or handheld by run or hike length. Plain-English guide to capacity, fit, bladder cleaning, and key features.
How to Set Up a Hydration Station (Office, Events, Youth Sports)
Step-by-step guide to planning a hydration station for offices, outdoor events, and youth sports—volume per person, placement, hygiene, and heat-day tips.
Hydration Breaks in the Heat: A Simple Schedule
OSHA- and NIOSH-backed hydration break schedules for hot weather. Learn how often to drink, how much, and warning signs to watch for.
Do You Really Need Electrolytes? FAQ
Water vs electrolyte drinks, sugar, keto, kids, pregnancy and hyponatremia — plain answers to your top hydration electrolytes questions.