Water Intake Calculator
Calculate how much water you should drink per day based on your weight, activity level, and climate conditions.
Staying properly hydrated is crucial for optimal health, energy levels, and physical performance.
Frequently Asked Questions
How much water should I drink?
A common guideline is 8 glasses (64 oz) per day, but individual needs vary. A more personalized approach is 30-35ml per kg of body weight, adjusted for activity level, climate, and health conditions.
Does coffee count as water intake?
Yes, coffee and tea contribute to daily fluid intake despite their mild diuretic effect. However, water is best for hydration. Aim for at least half your fluid intake from plain water.
How do I know if I'm dehydrated?
Signs of dehydration include dark yellow urine, dry mouth, fatigue, dizziness, and headaches. Urine should be pale yellow. Thirst is a late sign of dehydration, so drink water regularly throughout the day.
This is not medical advice — talk to your doctor. The sections below are educational only. Water targets are estimates based on standard formulas; actual needs vary with health, climate, and activity. People with kidney, heart, or fluid-restriction conditions should follow a doctor's limits, not a calculator.
Your Morning-to-Night Hydration Schedule
Drinking your daily target all at once is hard on the body and can disrupt sleep. Instead, spread it across the day. This sample schedule adds up to about 2.5 L — adjust the amounts up or down to match the number the tool gives you:
| Time | Amount | Why |
|---|---|---|
| 7:00 AM | 500 ml | Rehydrate after sleep; kick-starts metabolism |
| 9:00 AM | 250 ml | Mid-morning sip with breakfast |
| 11:00 AM | 350 ml | Pre-lunch top-up |
| 1:00 PM | 400 ml | With lunch; aids digestion |
| 3:00 PM | 350 ml | Afternoon energy dip; combat fatigue |
| 5:00 PM | 350 ml | Pre-evening; supports activity |
| 7:00 PM | 250 ml | With dinner |
| 9:00 PM | 100 ml | Small sip; limit to protect sleep |
| Total | ~2.55 L | Scale to your target |
Tip: the bulk of your intake is done by late afternoon. The evening amount is small on purpose so you are not up all night.
The Daily Water Intake Formula
The tool above runs a simple, transparent formula:
Baseline = body weight (kg) × 30 to 35 ml
Activity add-on = +350 to 500 ml per hour of exercise
Climate add-on = +500 ml or more in hot/humid weather
For the full general water-intake guide, see theWater Intake Calculator page.
How Much Water by Body Weight
Baseline daily intake before activity adjustments:
| Body weight | Baseline (liters) | Baseline (ounces) |
|---|---|---|
| 50 kg (110 lb) | 1.5 to 1.75 L | 51 to 59 oz |
| 60 kg (132 lb) | 1.8 to 2.1 L | 61 to 71 oz |
| 70 kg (154 lb) | 2.1 to 2.45 L | 71 to 83 oz |
| 80 kg (176 lb) | 2.4 to 2.8 L | 81 to 95 oz |
| 90 kg (198 lb) | 2.7 to 3.15 L | 91 to 107 oz |
| 100 kg (220 lb) | 3.0 to 3.5 L | 101 to 118 oz |
Add 350 to 500 ml per hour of exercise and more in hot weather.
Worked Example: A 70 kg Day
A 70 kg adult who does 45 minutes of moderate exercise in a mild climate:
- Baseline = 70 kg × 35 ml = 2,450 ml (2.45 L)
- Exercise add-on = 45 min ≈ 400 ml
- Daily target ≈ 2.85 L (about 96 oz)
- Spread across the schedule above: ~500 ml on waking, steady sips through the day, ~250 ml around the workout, and a small sip before bed.
Run your own numbers in the tool, then map the total onto the schedule.
How to Use This Calculator
- Enter your body weight in the tool above.
- Pick your activity level for the day.
- Note the daily target the tool returns.
- Open the morning-to-night schedule and scale each slot so the total matches your target.
- Use a reusable bottle with volume marks to hit each slot without measuring.
What to Do With Your Result
- Check urine color. Pale yellow means you are on track; dark yellow means drink more.
- Adjust for heat and sweat. Add 500 ml or more on hot days or during long workouts.
- Do not chug. Sip steadily; drinking too much too fast can be unsafe.
- Recalculate when weight changes. A 10 kg shift changes your baseline by about 300 to 350 ml.
- Watch for dehydration signs. See the Dehydration Calculator to assess your risk.