Water Bottle Sizes in Ounces and Milliliters
Common water bottles hold 12 to 48 fluid ounces, and a 32 oz bottle is about 946 mL; the right size depends on how often you can refill it during the day.
By Adolph GreenContributing writer.
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The short answer
Reusable water bottles are sold by US fluid ounces. Nalgene, for example, sells 12, 16, 24, 32 and 48 oz bottles. One fluid ounce is 29.57 milliliters, according to NIST's conversion table, so a 32 oz bottle holds about 946 mL, just under a liter. Choose the size by how often you can refill: a small bottle is fine at a desk next to a tap, while a long hike or shift without water calls for a larger one.
How many ounces in a water bottle?
| Bottle size | Milliliters (about) | Liters (about) |
|---|---|---|
| 12 oz | 355 mL | 0.35 L |
| 16 oz | 473 mL | 0.47 L |
| 20 oz | 591 mL | 0.59 L |
| 24 oz | 710 mL | 0.71 L |
| 32 oz | 946 mL | 0.95 L |
| 40 oz | 1,183 mL | 1.18 L |
| 48 oz | 1,419 mL | 1.42 L |
The metric figures are our own math with the NIST factor.
How much water do you need in a day?
The National Academies' 2004 report on water set adequate intake at about 2.7 liters (91 ounces) of total water a day for women and 3.7 liters (125 ounces) for men. That total counts water from food as well as drinks, and the report puts drinks at about 80 percent of it. Very active people in hot weather may need far more; the report cites total needs of six liters or more for some. It also says that for most people, drinking when thirsty and with meals keeps them hydrated.
32 oz vs 40 oz water bottle
Using the report's averages, drinks supply roughly 73 oz a day for women and 100 oz for men (80 percent of the totals, our math). Here is how many fills that takes:
| 32 oz bottle | 40 oz bottle | |
|---|---|---|
| Women, about 73 oz from drinks | about 2.3 fills | about 1.8 fills |
| Men, about 100 oz from drinks | about 3.1 fills | about 2.5 fills |
A 40 oz bottle saves roughly half a refill a day. A 32 oz bottle carries 8 oz (about 237 mL) less water, so it is lighter and smaller to carry. If you can refill at work or school, the smaller bottle is usually enough.
How often to replace a water bottle
Nalgene does not set a replacement schedule. It says its bottles are made to last and backs them with a lifetime guarantee against functional damage such as cracks, breaks or broken parts from normal use; scratches and worn prints are cosmetic and not covered. In practice, replace a bottle or its lid when it cracks, leaks or a part breaks, and clean it regularly: Nalgene says its bottles are dishwasher safe on the top rack and gives a hand-wash method with warm water and a few drops of bleach. If you freeze a bottle, fill it only about two-thirds to leave room for expansion.
How we count
Of the 76 sports water bottles listed on Wiki Shopping on October 26, 2026, 43 state a size we can read: 19 at 32 oz, 8 at 24 oz, 7 at 20 oz, 5 at 16 oz and 4 at 12 oz.
Shopping on Wiki Shopping
Water bottles sit in the sports and outdoors department. Check the capacity on the store page in both ounces and milliliters.