Buying guide
How many water bottles a day should you drink?
Using the National Academies' water intake figures: about 2.5 Stanley-size 40 oz bottles a day for men and about 1.9 for women. Bottle-by-bottle refill math.
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Using the National Academies' adequate intake from beverages (about 3.0 L, or 101 oz, for men and 2.2 L, or 74 oz, for women), that's roughly 2.5 × 40 oz or 4.2 × 24 oz bottles a day for men, and 1.9 × 40 oz or 3.1 × 24 oz for women. Exercise and heat raise the number.
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Where do these numbers come from?
The National Academies set adequate intakes for total water at 3.7 L/day for men and 2.7 L/day for women, and estimate that about 80% of it comes from drinks: 3.0 L and 2.2 L (National Academies). Mayo Clinic cites the same 2.7–3.7 L range and notes that food provides about 20% (Mayo Clinic). These are population averages, not personal prescriptions.
How many refills is that per bottle size?
| Bottle | Men (101 oz) | Women (74 oz) |
|---|---|---|
| 12 oz | 8.5 | 6.2 |
| 24 oz | 4.2 | 3.1 |
| 32 oz | 3.2 | 2.3 |
| 40 oz | 2.5 | 1.9 |
| 64 oz | 1.6 | 1.2 |
Computed from 3.0 L and 2.2 L (1 oz = 29.57 mL).
Does coffee or tea count?
Yes. Mayo Clinic says tea, coffee and milk count toward your daily fluids (Mayo Clinic). Our calculator lets you subtract them.
How much extra should you drink when exercising?
The American Council on Exercise suggests 7–10 oz every 10–20 minutes during exercise (ACE). Our calculator uses the low end, 7 oz per 20 minutes, as a conservative add-on.
Frequently asked questions
Is a 40 oz bottle a day enough water?
For most adults it's less than the National Academies' adequate intake from beverages (74 oz for women, 101 oz for men), though food and other drinks also count.
Can you drink too much water?
Yes, though it's rare. Mayo Clinic notes that drinking too much can cause hyponatremia (low sodium), which can be life-threatening.
Sources
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