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How to work out how much water to drink a day

You want a daily water target that fits your body and your day, not a flat eight glasses. You will enter weight, exercise minutes and climate and read litres and glasses. A 70 kg person with 30 minutes of exercise in a temperate climate gets about 2.8 litres. Nothing leaves this tab.

6-minute read

Today's result Total water a day in litres and 250 ml glasses, split into the part from body weight, from exercise and from climate.

Open the water intake calculator with your weight at hand. Count tea, coffee, milk and food toward the total. A rule of thumb for healthy adults, not medical advice. Nothing is uploaded.

Open Water intake calculator
Contents

  1. Know the rule of thumb

    About 35 ml per kilogram of body weight a day covers a healthy adult at rest in mild weather. Exercise adds roughly 12 ml per minute (360 ml per half hour). Hot or humid weather adds about half a litre.

    35 ml × kg, plus 12 ml × exercise minutes, plus 500 ml in heat.
    35 ml × kg, plus 12 ml × exercise minutes, plus 500 ml in heat.

  2. Open Water intake calculator on cv.cm

    70 kg, 30 minutes of exercise and a temperate climate are set. The total sits on the right. Nothing is uploaded.

    Open Water intake calculator

  3. Enter your weight

    Type the weight in kg, or switch the unit to lb. 70 kg gives a base of 2450 ml; 60 kg gives 2100 ml.

  4. Add exercise minutes

    Enter the minutes of exercise on a typical day. 30 minutes adds 360 ml; an hour adds 720 ml. Use 0 on rest days.

    70 kg and 30 minutes: 2450 + 360 = 2810 ml, about 12 glasses of 250 ml.
    70 kg and 30 minutes: 2450 + 360 = 2810 ml, about 12 glasses of 250 ml.

  5. Set the climate

    Pick Hot or humid in summer or in the tropics to add 500 ml. For 70 kg, 30 minutes and hot weather the total is 3.31 litres, 14 glasses.

  6. Spread it through the day, then copy

    12 glasses is one every hour or so while awake; thirst and pale urine are the simple checks. Copy puts the breakdown on the clipboard.

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FAQ

Can I calculate my water intake free online?

Yes. cv.cm computes it in this tab. Nothing is uploaded.

How much water should a 70 kg person drink?

About 2.45 litres at rest, 2.8 litres with 30 minutes of exercise, and 3.3 litres in hot weather.

Do coffee and tea count?

Yes. They are mostly water. Food also supplies roughly a fifth of daily fluid.

Is eight glasses a day right?

Eight 250 ml glasses is 2 litres, which fits a 57 kg person at rest. Heavier, active people need more; the calculator scales it.

Is this medical advice?

No. Pregnancy, breastfeeding, kidney or heart conditions and some medicines change the need. Ask a doctor.