How much water should you drink per day? (Hydration guide)
Use this water intake calculator as a practical starting point, then refine your daily target using real-world feedback (thirst, urine color, performance, and sweat losses). The goal is sustainable hydration—not forcing a fixed number.
Quick method (what this calculator uses)
A simple evidence-informed baseline is 30–35 ml per kg of body weight per day, with adjustments for exercise and hot/humid weather.
- Baseline: 0.03–0.035 L/kg/day (example: 70 kg → ~2.1–2.45 L/day)
- Exercise: add fluid for sweat losses (often ~0.5–1.0 L per hour, varies)
- Heat/humidity: add extra (sweat increases, and losses rise quickly)
Tip: If you’re doing endurance training, consider adding electrolytes (especially sodium) instead of only increasing plain water.
Daily water intake examples (by body weight)
These are starting points. Sweat rate varies hugely with intensity, clothing, body size, and environment. If you’re consistently very thirsty post-workout or have dark urine for hours, you may need more fluids (and possibly electrolytes).
| Body weight | Baseline (30–35 ml/kg) | Baseline (fl oz) | + 1h exercise (rough) | + hot/humid day (rough) |
|---|---|---|---|---|
| 50 kg (110 lb) | 1.5–1.75 L | 51–59 oz | ≈ +0.5–1.0 L | ≈ +0.5–1.0 L |
| 60 kg (132 lb) | 1.8–2.1 L | 61–71 oz | ≈ +0.5–1.0 L | ≈ +0.5–1.0 L |
| 70 kg (154 lb) | 2.1–2.45 L | 71–83 oz | ≈ +0.5–1.0 L | ≈ +0.5–1.0 L |
| 80 kg (176 lb) | 2.4–2.8 L | 81–95 oz | ≈ +0.5–1.0 L | ≈ +0.5–1.0 L |
| 90 kg (198 lb) | 2.7–3.15 L | 91–107 oz | ≈ +0.5–1.0 L | ≈ +0.5–1.0 L |
| 100 kg (220 lb) | 3.0–3.5 L | 101–118 oz | ≈ +0.5–1.0 L | ≈ +0.5–1.0 L |
Hydration signals: quick self-check table
Note: vitamins/supplements and some medications can change urine color. Use multiple signals, not just one.
| Signal | Often OK | Often needs attention |
|---|---|---|
| Urine color | Pale yellow | Dark yellow / amber (persisting) |
| Thirst | Mild / occasional | Strong / frequent |
| Energy & focus | Stable | Fatigue, headache, irritability |
| During exercise | Normal performance | Early fatigue, cramps (can be electrolytes too) |
Caution: overhydration and hyponatremia (rare, but important)
More is not always better. Very rapid, very large water intake can dilute blood sodium (hyponatremia), especially during long endurance events. If you’re training for long durations, consider:
- Drinking to a plan informed by sweat losses (or thirst) rather than “as much as possible”
- Including sodium/electrolytes when sweating heavily
- Not trying to “force-clear” urine all day
Related calculators (useful together)
- TDEE Calculator — daily energy needs (hydration often drops when dieting aggressively).
- BMI Calculator — quick screening metric; not hydration-specific but helpful context.
- Calorie Burn Calculator — more activity usually means more sweat and fluid needs.
Interesting hydration facts (quick wins)
- You don’t need to “hit a perfect number”: consistency matters more than precision.
- Food contributes: many fruits/vegetables are mostly water, which supports total fluid intake.
- Sweat loss is individual: two people doing the same workout can have very different needs.