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Water Intake Calculator

Find out exactly how much plain water you should drink today, based on your body weight, activity level and climate — plus a personalised drinking schedule for the day.

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Daily Water Intake Calculator

Please enter a valid body weight to calculate.

The Method

How We Calculate Your Water Intake

General Adult Guideline

Base = Weight(kg) × 33 ml + Activity adjustment (0–1000 ml) + Climate adjustment (0–600 ml)

This scales with your actual body size rather than giving everyone the same flat number, and adjusts upward for exercise and heat — the two biggest everyday drivers of extra fluid loss.

Worked Example

Step-by-Step Example

A 65 kg adult, lightly active, in a mild climate.

1
Base: 65 × 33 = 2,145 ml
2
Add activity: + 350 ml (light) = 2,495 ml
3
Add climate: + 0 ml (mild) = 2,495 ml
4
Total: ≈2.5 litres/day ≈ 10 glasses (250 ml each)
Quick Reference

Common Water Targets in Glasses & Bottles

Daily TargetGlasses (250 ml)Bottles (500 ml)Bottles (1 L)
2.0 L842
2.5 L1052.5
3.0 L1263
3.5 L1473.5
4.0 L1684
Stay on Track

Tips for Hitting Your Water Target

Start With a Glass on Waking

You lose fluid overnight through breathing and sweat — a glass of water first thing helps you start the day ahead.

Carry a Marked Bottle

A bottle with time markers makes it easy to see at a glance whether you're on pace for the day.

Pair Water With Habits

Drink a glass before each meal and after each bathroom break to build a consistent, automatic routine.

Front-Load Earlier in the Day

Drinking more in the morning and afternoon, less in the evening, avoids disrupting sleep with night-time bathroom trips.

Increase Around Exercise

Add extra water before, during and after workouts to replace what you lose through sweat.

Watch Urine Colour

Pale yellow generally indicates good hydration; consistently dark yellow suggests you need more water.

Questions

Frequently Asked Questions

It depends on your weight, activity level and climate, but most adults land somewhere between 8 and 14 glasses (250 ml each). Use the calculator above for a number based on your own body weight rather than a generic average.
Yes — this tool calculates a target for plain water specifically. If you want to track your total fluid intake including tea, coffee, milk and other drinks, use our Liquid Intake Calculator instead, which includes a full daily beverage log.
Your total daily target is split evenly across roughly 8 intervals from your wake-up time through the evening, so you drink steadily through the day instead of trying to catch up all at once.
Yes. Sweat losses during exercise add to your baseline fluid needs, which is why the calculator includes an activity-level adjustment on top of your body-weight baseline.
Heat and humidity increase sweat rate, so your body loses more fluid than usual even at rest — the climate adjustment accounts for this.
Thirst is a lagging indicator — by the time you feel thirsty, mild dehydration has often already started. Spreading intake evenly through the day (like the schedule above) helps you stay ahead of it.
In rare cases, drinking very large volumes in a short time can dilute blood sodium levels (hyponatremia). This is uncommon with normal drinking patterns spread across the day.
No. All calculations run entirely in your browser for this session — nothing is sent to or stored on our servers.

Ready to Build a Water-Drinking Habit?

Calculate your target above, then follow your personalised schedule through the day.

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