AnyTool
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How much water should I drink a day for my weight?

Enter your body weight in AnyTool Water Intake Calculator (metric kg or imperial lb) and it estimates your daily fluid target from a body-weight baseline of about 33 ml per kilogram — the metric twin of the U.S. “half your weight in pounds, in fluid ounces” rule. It then adds roughly 12 fl oz (≈355 ml) for every 30 minutes of exercise, raises the total about 12.5% for hot, humid days, and can add the pregnancy (+300 ml) or breastfeeding (+700 ml) increment. Results are shown in litres, US cups, fluid ounces and 240 ml glasses, plus a “total incl. food” figure, and everything is calculated in your browser so nothing is uploaded.

  • Baseline ≈ 33 ml of fluid per kg of body weight (the 30–35 ml/kg rule)
  • Adds ~12 fl oz (≈355 ml) per 30 minutes of exercise
  • Hot/humid climate +~12.5%; cold trimmed slightly
  • Optional pregnancy +300 ml or breastfeeding +700 ml
  • 100% in your browser — no upload, no signup, works offline

What is

Daily Water Intake

Daily water intake is the total fluid your body needs each day to stay hydrated, commonly estimated from body weight at roughly 30–35 ml per kilogram for healthy, sedentary adults in a temperate climate, then adjusted upward for exercise, heat, pregnancy and breastfeeding. About 80% of total water usually comes from drinks and the other 20% from food, so a drinks target is lower than total water intake. As a reference, the U.S. National Academies (NASEM) set adequate-intake totals — drinks plus food — of about 2.7 L/day for women and 3.7 L/day for men.

Calculators

Related terms

Hydrationml per kg ruleNASEM adequate intakeElectrolytes

Frequently Asked Questions

A common rule is about 30–35 ml of water per kilogram of body weight, so a 70 kg adult needs roughly 2.3 litres a day from drinks before adding exercise and heat.

A widely taught estimate is 30–35 ml of fluid per kilogram of body weight per day for a healthy, sedentary adult — this calculator uses 33 ml/kg, so a 70 kg person gets about 2.3 L. That is the metric equivalent of the U.S. rule of drinking half your body weight in pounds as fluid ounces. On top of the baseline AnyTool adds about 12 fl oz (355 ml) for every 30 minutes of exercise and raises the total for hot or humid weather, all live as you type.

Add roughly 12 fl oz (about 355 ml) for every 30 minutes of exercise, and bump your whole target up around 10–15% on hot, humid days.

Sweat loss during activity and heat means you need more fluid. A practical guide is to add about 12 fl oz (≈355 ml) per 30 minutes of moderate-to-vigorous exercise, scaled by how long you train, and to raise your total daily target by roughly 10–15% in hot or humid conditions. AnyTool applies a 12.5% hot-climate bump and lets you enter your exercise minutes so the extra is built in automatically.

Yes — about 20% of your daily water normally comes from food, so your total water intake is higher than what you drink.

According to the U.S. National Academies, roughly 80% of total water intake comes from drinks and about 20% from food such as fruit, vegetables and soups. This calculator gives you a target for fluid to drink and also shows a “total incl. food” figure so you can compare with the NASEM adequate-intake totals of about 2.7 L/day for women and 3.7 L/day for men, which count both food and drink.

Yes — drinking very large volumes quickly can dangerously dilute blood sodium (hyponatraemia), so use the estimate as a guide and follow thirst.

Hydration needs are individual, and over-drinking is a real risk: consuming far more water than your kidneys can clear, especially quickly, can lower blood sodium to dangerous levels (hyponatraemia). Treat the calculator as an estimate, let thirst and pale-yellow urine guide you, and if you have kidney, heart or liver disease or have been told to restrict or load fluids, follow your clinician rather than a formula. AnyTool runs entirely in your browser, so your details are never sent anywhere.

Detailed Explanation

Methodology

How the Water Intake Calculator Works

AnyTool Water Intake Calculator estimates a daily fluid target in the browser from body weight, using a baseline of about 33 ml of fluid per kilogram (the midpoint of the widely taught 30–35 ml/kg range), which is the metric equivalent of the U.S. rule of drinking half your body weight in pounds as fluid ounces. It then adds roughly 355 ml (~12 US fl oz) for every 30 minutes of exercise entered, multiplies the subtotal by a climate factor (1.0 temperate, 1.125 hot/humid, 0.97 cold), and adds optional flat life-stage increments of 300 ml for pregnancy or 700 ml for breastfeeding. The output is the fluid to drink; because about 20% of total water normally comes from food, the engine also reports a higher total-water figure. All arithmetic is pure client-side JavaScript shared through a unit-tested engine.

  • Baseline = body weight × ~33 ml/kg (the 30–35 ml/kg rule)
  • Equivalent to the U.S. half-your-weight-in-pounds-as-ounces rule
  • Exercise adds ~355 ml per 30 minutes, scaled by minutes entered
  • Climate factor: 1.0 temperate, 1.125 hot/humid, 0.97 cold
  • Optional +300 ml pregnancy / +700 ml breastfeeding increments
How It Works

Units, Food Water and Reference Intakes

The recommended target is shown in litres, millilitres, US cups (240 ml), US fluid ounces (29.5735 ml) and standard 240 ml glasses, with a friendly glass-and-bottle visualisation. Because drinks supply only about 80% of total water and food the other 20%, the calculator also reports the implied total water intake (target ÷ 0.8) so users can compare against the U.S. National Academies (NASEM) adequate-intake totals of roughly 2.7 L/day for women and 3.7 L/day for men, which count both food and drink for healthy, sedentary adults in a temperate climate. Those NASEM figures are reference points for typical needs, not hard limits.

  • Results in litres, ml, US cups, fl oz and 240 ml glasses
  • About 80% of total water comes from drinks, 20% from food
  • Total-water figure = drinks target ÷ 0.8
  • NASEM adequate intake: ~2.7 L/day women, ~3.7 L/day men (food + drink)
  • Reference totals are sedentary, temperate-climate baselines
Limitations

An Estimate, Not Medical Advice

Real fluid needs are highly individual, driven by sweat rate, diet, illness, medication and the weather, so the calculator presents a starting estimate rather than a prescription and advises following thirst and urine colour. It warns against over-drinking, since consuming very large volumes quickly can dilute blood sodium and cause hyponatraemia, and it states that people with kidney, heart or liver disease — or anyone told to restrict or load fluids — should follow their clinician rather than a formula. AnyTool discloses these limits plainly on the page.

  • Needs vary with sweat, diet, illness, medication and weather
  • Thirst and pale-yellow urine are good real-time guides
  • Over-drinking can cause dangerous hyponatraemia
  • Kidney, heart or liver patients should follow their clinician
  • Presented as guidance, not a diagnosis or prescription
Privacy & Security

Privacy and Offline Use

Because all computation runs in the browser, your weight, activity and life-stage details are never sent to a server, there is no account or tracking, and the page works offline after first load. The calculator is built on a shared, unit-tested water-intake engine so its behaviour is consistent and verifiable.

Water intake estimate: in-browser (AnyTool) vs typical online hydration calculators
CapabilityAnyToolTypical online calculators
ProcessingRuns in your browserOften server-side
Unitskg or lb input; L, ml, cups, fl oz, glasses outUsually one or two units
ActivityPer-minute exercise adjustmentOften a coarse activity level
ClimateHot / temperate / cold factorFrequently ignored
Life stagePregnancy and breastfeeding incrementsUsually none
Food waterShows total incl. ~20% from foodRarely shown
HonestyOver-drinking + medical caveats statedOften omitted
Works offlineYes (PWA)No
Cost / signupFree, no signupOften ad-heavy or gated

AnyTool computes the hydration estimate locally and uploads nothing; needs are individual and the result is guidance, not medical advice.