Water intake calculator

Estimate your daily water intake target.

Last updated: January 10, 2026

Built and maintained by Aaron Jegla

Methodology aligned with hydration guidance from the National Academies of Sciences and exercise hydration standards from ACE. This tool is not a substitute for medical advice.

Estimate total daily water needs, a drink target, and an hourly plan using sex at birth, life stage, and activity inputs. Built for adults 19+ who want a clear hydration baseline.

Hydration inputs

Adequate intake baselines differ by sex and life stage.

Uses higher adequate intake targets for pregnancy or lactation.

Only include moderate or hard workouts.

Uses a 0.4 to 0.8 L per hour range.

Used to pause the hourly plan during sleep and the final 2 hours before bed.

Adds a small adjustment for movement-heavy days.

Best for healthy adults 19+ who want a baseline hydration target.

Not for fluid-restricted conditions; follow medical guidance. Explore health calculators.

How to use this calculator
  1. Select sex at birth and a life stage if needed.
  2. Add daily exercise minutes, a sweat level, workday activity, and your sleep time.
  3. Click Calculate to see your targets and hourly plan.

Adjust for heat, altitude, and heavy sweating in real life.

Summary

Activity add-on combines workday movement and exercise.

Total water target

0 L (0 oz)

Drink target

0 L (0 oz)

Activity add-on

0 L (0 oz)

Daily cups (8 oz)

0 cups

About 0 oz per hour across your typical awake hours.

Sources: National Academies: Dietary Reference Intakes for water, ACE hydration guidance for exercise, Sleep Foundation: hydration and sleep

Assumptions: Adequate intake targets for adults 19+, with pregnancy and lactation adjustments. Assumes about 20% of total water comes from food. Workday activity adds 0.0 to 0.6 L. Exercise fluids use the 0.4 to 0.8 L per hour range and scale by your minutes and sweat level. Hourly pacing assumes 8 hours of sleep and reduces fluids in the 2 hours before bedtime.

Reality check: Use thirst and pale-yellow urine as quick feedback and adjust for heat or heavy sweating.

Medical note: If you have kidney, heart, or fluid-restriction conditions, follow clinical guidance instead of general targets.

Disclaimer: Estimates only and not medical advice.

Who should not use this calculator: This tool is intended for healthy adults 19+. It is not appropriate for people with kidney disease, heart failure, fluid-restricted conditions, or those under medical hydration protocols.

Hourly hydration recommendation

Each hour shows your pacing target and pauses during sleep and the last 2 hours before bed.

12:00 AM 0 oz
1:00 AM 0 oz
2:00 AM 0 oz
3:00 AM 0 oz
4:00 AM 0 oz
5:00 AM 0 oz
6:00 AM 0 oz
7:00 AM 0 oz
8:00 AM 0 oz
9:00 AM 0 oz
10:00 AM 0 oz
11:00 AM 0 oz
12:00 PM 0 oz
1:00 PM 0 oz
2:00 PM 0 oz
3:00 PM 0 oz
4:00 PM 0 oz
5:00 PM 0 oz
6:00 PM 0 oz
7:00 PM 0 oz
8:00 PM 0 oz
9:00 PM 0 oz
10:00 PM 0 oz
11:00 PM 0 oz

Sleep hours and the pre-bed window show 0 oz so you can see where intake pauses.

How this calculator works

It starts with national adequate intake targets and adds daily activity adjustments.

Adequate intake baseline

Baseline = 3.7 L (men) or 2.7 L (women)

Pregnancy uses 3.0 L and breastfeeding uses 3.8 L as total water from all sources.

  • Targets are for adults 19+.
  • They include fluids from beverages and food.
Workday activity adjustment

Work add-on = 0.0 to 0.6 L

More time on your feet usually means more daily fluid needs.

  • Mostly seated: 0.0 L.
  • On your feet sometimes: 0.3 L.
  • Active/manual work: 0.6 L.
Exercise add-on

Exercise add = (minutes / 60) * rate

Rate is based on your sweat level and stays within 0.4 to 0.8 L per hour.

  • Light sweat: 0.4 L per hour.
  • Moderate sweat: 0.6 L per hour.
  • Heavy sweat: 0.8 L per hour.
Drink target

Drink target = total water * 0.8

This assumes about 20% of total water comes from food.

  • The drink target is for beverages only.
  • Soups, fruits, and vegetables still count toward total water.
Hourly pacing

Hourly target = drink target / 14 hours

We assume 8 hours of sleep and pause the final 2 hours before bed.

  • Use the hourly number as a pacing guide.
  • Shift intake earlier if you sleep sooner.

Hydration insights and common misses

Use these notes to personalize the estimate.

Food counts too

Fruits, vegetables, and soups add meaningful water.

  • The drink target is only the beverage portion.
  • Hydrating foods help you reach the total.

Sweat rate changes fast

Heat, humidity, and clothing shift how much you sweat.

  • Add more water on hot or high-output days.
  • Re-check after schedule changes.

Thirst lags behind need

Thirst is useful but can show up late during busy days.

  • Use the split plan to pace intake.
  • Check urine color for a quick signal.

Long workouts need more

Sessions over an hour usually need extra fluids.

  • Consider electrolytes if you sweat heavily.
  • Drink before and after long sessions.

Big chugs are hard to stick with

Large boluses can cause discomfort or bathroom overload.

  • Use smaller, regular amounts.
  • Match intake to your routine.

Too much water is possible

Overhydration can dilute sodium if intake is extreme.

  • Spread intake across the day.
  • Avoid forcing large volumes quickly.

Water intake calculator FAQs

Click a question to expand the answer.

Is the 8x8 rule accurate?

It is a simple rule of thumb, but needs vary. This calculator uses adequate intake guidelines and adds exercise fluids so the target adjusts to your routine.

Do coffee, tea, or sparkling water count?

Yes. Most non-alcoholic beverages count toward daily fluid intake. If you drink alcohol, add extra water because it can increase fluid loss.

How much extra water should I drink during exercise?

General guidance is about 0.4 to 0.8 liters per hour of exercise, depending on sweat rate. This calculator uses that range and scales it to your minutes and intensity.

Should I drink more in hot weather?

Usually, yes. Heat and humidity increase sweating, so your needs go up. Use thirst and urine color as real-world checks and add water if you are sweating more than usual.

Can you drink too much water?

Yes. Drinking large amounts in a short time can dilute sodium levels. Spread intake across the day and avoid forcing extreme volumes.

Does water intake change with age?

Thirst cues can weaken with age, so older adults may need to be more intentional about fluids. If you have medical conditions or take diuretics, follow clinical guidance.

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