💧 Water Intake Calculator
Enter your body weight, today's activity, and the climate to see how much water you should be drinking — in liters, milliliters, and glasses — before you head back out on the water.
🚰 Estimate Your Daily Water Target
What is a Water Intake Calculator?
It gives you a quick, personalized hydration target instead of relying on a generic "eight glasses a day" rule. Enter your weight, your activity minutes, and the climate you're in, and it scales your baseline water need up for exertion and heat, then breaks the total down into liters, milliliters, and standard glasses so it's easy to track through the day.
It's especially useful for sailors and anyone else spending long hours on deck: sun, wind, and humidity all increase fluid loss in ways that are easy to underestimate when a constant breeze keeps you feeling cool. Use it before a long day on the water to plan how much to bring, and treat the result as a starting point — not a substitute for listening to your body or medical guidance.
❓ Frequently Asked Questions
How does the water intake calculator work?
Enter your body weight, how many minutes of activity you've done today, and the climate you're in. It starts from roughly 33ml of water per kilogram of body weight, adds around 350ml for every 30 minutes of activity, then applies a bonus for hot or humid conditions before converting the total into liters, milliliters, and standard 250ml glasses.
Why do sailors need more water than people on land?
Sun, wind, and salt spray all accelerate fluid loss, and the constant breeze on deck can mask how much you're actually sweating — so it's easy to underestimate how dehydrated you're getting. Time spent hauling lines, trimming sails, or simply standing watch in direct sun adds up fast, which is why activity minutes and climate both push your target higher.
Does hot or humid weather really change how much I should drink?
Yes. In hot conditions your body sweats more to cool itself, and in humid conditions that sweat evaporates less efficiently, so you sweat even more to compensate. This calculator adds roughly a 10% bonus for hot climates and 15% for hot, humid ones on top of your base and activity needs.
Is this medical advice?
No. This tool gives a general, informational estimate only — actual hydration needs vary by individual (sweat rate, body composition, medications, and underlying health conditions). Drink to thirst, watch for signs of dehydration or heat illness, and speak to a doctor if you have a condition that affects fluid intake.