Daily Water Intake
Calculator
Get a precise, personalised hydration target based on your body weight, activity level, climate, and health conditions. Go beyond the "8 glasses a day" myth.
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All factors below affect your optimal hydration needs.
Enter your details and press calculate to see your personalised hydration target.
Why Water Is the Most
Underrated Health Tool
Your body is approximately 60% water. Every single physiological process — from digestion to cognition to temperature regulation — depends on adequate hydration. Yet chronic mild dehydration is one of the most widespread and overlooked health issues.
Recognising Dehydration — From Mild to Severe
Thirst is a late indicator — by the time you feel thirsty, you're already mildly dehydrated. Understanding the stages helps you stay ahead of the curve.
- Slight thirst sensation
- Marginally reduced focus
- Slightly darker urine
- Easily overlooked
- Noticeable thirst
- Reduced short-term memory
- Headache onset
- Decreased endurance
- Dry mouth
- Significant headache
- Fatigue & lethargy
- Muscle weakness
- Nausea possible
- Dark amber urine
- Reduced urine output
- Extreme thirst
- Dizziness & confusion
- Rapid heart rate
- Muscle cramps
- No urination
- Medical attention needed
- Loss of consciousness
- Seizures possible
- Organ failure risk
- Requires IV fluids
- Call emergency services
The Urine Colour Chart
The easiest free hydration monitor is already built into your body. Urine colour provides an instant, real-time readout of your hydration status throughout the day.
Note: Some foods (beetroot, asparagus) and medications can alter urine colour independently of hydration status.
Daily Water Intake Reference Table
Compare your result against these evidence-based estimates for common profiles. Values represent total daily water intake including all sources.
| Profile | Sedentary | Lightly Active | Moderately Active | Very Active | Hot Climate Add-on |
|---|---|---|---|---|---|
| Woman, 55 kg | 1.9 L | 2.2 L | 2.5 L | 2.9 L | +0.5–0.8 L |
| Woman, 65 kg | 2.1 L | 2.4 L | 2.8 L | 3.2 L | +0.5–0.8 L |
| Woman, 75 kg | 2.3 L | 2.7 L | 3.1 L | 3.6 L | +0.5–0.8 L |
| Man, 70 kg | 2.3 L | 2.7 L | 3.1 L | 3.6 L | +0.6–1.0 L |
| Man, 85 kg | 2.6 L | 3.0 L | 3.5 L | 4.1 L | +0.6–1.0 L |
| Man, 100 kg | 2.9 L | 3.4 L | 3.9 L | 4.6 L | +0.6–1.0 L |
| Pregnant woman | Base intake + 0.3–0.5 L/day above normal needs | +0.5–0.8 L | |||
| Breastfeeding woman | Base intake + 0.7–1.0 L/day above normal needs | +0.5–0.8 L | |||
| Elite endurance athlete | 4–6+ L/day depending on training duration and intensity | +1.0–2.0 L | |||
Sources: National Academies of Medicine, WHO, European Food Safety Authority (EFSA). Values include water from all dietary sources.
Water Content in Common Foods
Approximately 20–30% of daily water intake comes from food. Eating a diet rich in fruits and vegetables significantly contributes to your hydration without you ever picking up a glass.
How to Actually Hit Your Water Target
Knowing how much to drink is half the battle. Here are the most effective evidence-based strategies for building a hydration habit that sticks.
Start With 500ml On Waking
After 7–9 hours of sleep your body is mildly dehydrated. Drinking 500ml first thing — before coffee, before your phone — kick-starts metabolism and sets a hydrating tone for the day.
Drink on a Timed Schedule
Set phone reminders every 60–90 minutes rather than relying on thirst. By the time thirst signals fire, you're already 1–2% dehydrated. Habit-stacking (drink before every meal and meeting) works especially well.
Use a Marked Bottle
A 1-litre bottle with time markers (e.g., "by 12pm: 500ml") makes your target visible and creates accountability. Research shows marked bottles increase daily water intake by 40–60% on average.
Add Flavour to Fight Boredom
Infusing water with lemon, cucumber, mint, or berries makes plain water far more enjoyable. Herbal teas (hot or cold) count toward your target. Avoid squash and flavoured drinks with added sugar.
Eat Your Water Too
Build meals around high-water-content foods: start lunch with a salad or cucumber sticks, have watermelon or strawberries as a snack. This approach provides 400–600ml of additional water intake daily without drinking.
Electrolytes Matter During Exercise
Plain water is insufficient during intense or prolonged exercise. Sweat contains sodium, potassium, and magnesium. Add electrolyte tablets or coconut water to avoid hyponatraemia (dangerously low sodium from over-drinking plain water).
Track for 7 Days, Then Automate
Track water intake consciously for one week to calibrate your habits. After that, the urine colour chart provides all the real-time feedback you need. Consistent routines eliminate the need for constant tracking.
Don't Over-Drink Before Bed
Avoid large amounts of water within 90 minutes of sleep. Nocturia (waking to urinate) significantly reduces sleep quality. Taper intake in the evening and front-load drinking in the morning and afternoon.
Common Hydration Myths — Debunked
Much of what people "know" about hydration is oversimplified or flat-out wrong. Here's what the evidence actually says.
The "8×8" rule (eight 8-oz glasses) has no scientific basis. It was popularised from a misquoted 1945 guideline. Actual needs vary by 1.5–3× between individuals based on weight, activity, climate, and health status.
Moderate caffeine (up to 400mg/day) has a negligible net diuretic effect. Studies show habitual coffee drinkers develop tolerance. A cup of coffee contributes roughly 90% of its volume to hydration — not zero.
Thirst signals fire at approximately 1–2% dehydration — mild, not dangerous. It's still a lagging indicator, so don't rely solely on thirst, but experiencing thirst isn't a crisis. Drink when you feel it.
Very clear urine can indicate over-hydration, which dilutes electrolytes. Pale lemon-yellow is the optimal target — not transparent. Consistent clear urine alongside symptoms like headache may indicate low sodium (hyponatraemia).
The liver and kidneys handle detoxification regardless of water intake (as long as you're not chronically dehydrated). Adequate hydration supports these organs but doesn't supercharge them. Skin benefits are real but take weeks to appear.
Hyponatraemia (water intoxication) is a real, potentially fatal condition caused by drinking excessive amounts of plain water in a short period, diluting blood sodium. Most at risk: endurance athletes who drink enormous volumes during events without electrolytes.