Daily Hydration & Electrolyte Planner
Calculate personalized water and electrolyte needs based on activity. Enter values for instant results with step-by-step formulas.
Worked Examples
Example 1: Marathon Runner Hydration Plan
Problem:A 65kg runner is preparing for a marathon in warm weather (25°C). They sweat heavily and will be running for approximately 4 hours. Calculate hydration and electrolyte needs.
Solution:Pre-Race Analysis:\n- Weight: 65kg\n- Duration: 4 hours\n- Climate: Warm\n- Sweat rate: Heavy (~1.5L/hour estimated)\n\nBase Calculation:\n- Daily water: 65kg × 35ml = 2,275ml base\n- Activity adjustment: ×1.4 (athlete) = 3,185ml\n- Climate adjustment: ×1.15 (warm) = 3,663ml\n- Exercise addition: 4hr × 500ml × 1.15 = 2,300ml\n- Total race day: ~6L\n\nDuring Race (4 hours):\n- Target fluid: 500-800ml/hour = 2,000-3,200ml total\n- Sodium: 500-1000mg/hour (heavy sweater) = 2,000-4,000mg\n- Carbs: 30-60g/hour for energy\n\nRace Hydration Plan:\n- Pre-race (2 hrs before): 500ml with electrolytes\n- Pre-race (30 min): 200ml\n- During: 150-200ml every 15-20 minutes\n- Include: Sports drink alternating with water + salt tabs\n- Post-race: 1.5L per kg lost (weigh before/after)\n\nElectrolyte Strate
Result:6L race day total | 500-800ml/hr during | 2,000-4,000mg sodium | Sports drink + salt tabs
Example 2: Keto Diet Electrolyte Management
Problem:A person (80kg) just started a ketogenic diet and experiences fatigue, headaches, and muscle cramps ('keto flu'). They do moderate exercise 3x/week. Plan electrolyte supplementation.
Solution:Keto Electrolyte Analysis:\n\nWhy Keto Causes Electrolyte Issues:\n- Low insulin reduces sodium retention\n- Glycogen depletion releases water\n- Reduced processed food intake lowers sodium\n\nBase Requirements (80kg, moderate activity):\n- Water: 80 × 35 × 1.25 = 3,500ml/day\n- Standard sodium: 2,300mg\n- Standard potassium: 3,500mg\n- Standard magnesium: 400mg\n\nKeto-Adjusted Requirements:\n- Sodium: 2,300 + 1,000 = 3,300mg (some need 5,000-7,000mg)\n- Potassium: 3,500 + 500 = 4,000mg\n- Magnesium: 400 + 100 = 500mg\n\nSupplementation Plan:\n\nSodium:\n- Add salt to food liberally\n- Bone broth: 1-2 cups/day (500-1000mg)\n- Salt water: 1/4 tsp salt in water 2x/day (1,150mg)\n- Total supplemented: ~2,000-3,000mg\n\nPotassium:\n- Avocado (1/day): 700mg\n- Spinach (2 cups): 400mg\n- Supple
Result:3,300mg+ sodium | 4,000mg potassium | 500mg magnesium | Salt + broth + supplements
Example 3: Office Worker Basic Hydration
Problem:A sedentary office worker (75kg) in an air-conditioned environment wants to optimize hydration. They do 30 minutes of light exercise 3x/week. Current intake: ~4 cups of coffee plus some water.
Solution:Current State Assessment:\n- Weight: 75kg\n- Activity: Sedentary + light exercise\n- Climate: AC (effectively temperate/cool)\n- Current intake: Inadequate\n\nCoffee Consideration:\n- 4 cups coffee ≈ 400mg caffeine\n- Mild diuretic effect, but coffee does contribute to hydration\n- Net hydration from 4 cups ≈ 600ml\n\nCalculated Needs:\n- Base: 75kg × 35ml = 2,625ml\n- Activity adjustment: ×1.0 (sedentary) = 2,625ml\n- Exercise addition: 30min × 3/week ÷ 7 = ~13min/day avg\n- Exercise addition: negligible for planning\n- Total: ~2,600ml/day (2.6L)\n\nPractical Plan:\n\nWater Schedule:\n- Wake up: 500ml (before coffee)\n- Mid-morning: 400ml\n- Lunch: 300ml with meal\n- Afternoon: 500ml\n- End of workday: 400ml\n- Evening: 500ml\n- Total water: 2,600ml\n\nCoffee: Continue 4 cups (counts towa
Result:2.6L total daily | 8 additional cups beyond coffee | No supplements needed | Hourly reminders
Frequently Asked Questions
How much water should I drink daily?
A general guideline is 35ml per kg body weight (about 0.5oz per pound), adjusted for activity, climate, and individual factors. A 70kg person needs ~2.5L base, increasing with exercise and heat. Thirst isn't always reliable—monitor urine color instead.
When do I need electrolyte supplements?
Consider supplements when: exercising >60 minutes, sweating heavily, in hot/humid conditions, on low-carb diets, or experiencing symptoms like muscle cramps, fatigue, or headaches. For casual activity, a balanced diet usually provides sufficient electrolytes.
How does climate affect hydration needs?
Hot and humid conditions increase sweat rate dramatically—you may need 1.5-2x normal fluid intake. Cold weather reduces thirst sensation but dehydration still occurs. Altitude increases fluid needs due to increased respiration and urination.