How to convert your bottle size to milliliters

1. Convert your known bottle volume

Enter the capacity on the label, choose its unit and select the portion you finished. If you cannot tell which fluid-ounce system the label uses, check the manufacturer rather than guessing.

For a different portion, calculate label volume × unit factor × fraction consumed. For example, three quarters is 0.75. The tool cannot measure a fill level, spilled water or leftovers.

2. Check which ounce the label means

A US fluid ounce and an Imperial fluid ounce are different volumes. NIST’s conversion table gives approximately 29.57353 mL per US fl oz and 28.41306 mL per Imperial fl oz. Those published factors are rounded; the calculator uses them and rounds only the final consumed portion.

“oz” alone is not enough. Ounces can also measure weight. Do not use an ounce-by-weight number as a fluid volume, or silently assume an unlabeled fluid-ounce system is US. When a bottle prints both mL and fl oz, prefer its mL value; the printed equivalents may already be rounded.

Keep the unrounded number until the last step. Half of 16 Imperial fl oz is approximately 227.30448 mL, which becomes 227 mL. Halving the already rounded 455 mL gives 227.5 mL instead, enough to change the whole-milliliter result.

3. Separate capacity, leftovers and refills

Suppose a fictional 750 mL bottle starts full. You finish half, leaving 375 mL, then refill it. The first consumed amount is 375 mL; adding more water to the bottle does not mean you consumed a second full bottle.

If you later finish 250 mL after the refill, those two consumed amounts total 625 mL. Keep the earlier 375 mL record and add only the later 250 mL. Do not add a second 625 mL entry over both. Water poured away or left in the bottle is not part of the consumed record.

A fraction is useful only when it describes your actual portion. If you do not know the bottle’s capacity or how much remains, conversion arithmetic cannot make that estimate exact. For physical portion practice, use the separate cup-portion guide.

4. Enter the whole-milliliter amount in Frewli

1. On Today, open Other drink. The screen is called Add drink.
2. Choose Drink type > Water first. A new form normally starts with Coffee, and changing the type can reset the amount.
3. Enter the final whole number in Volume, whose empty-field prompt is Milliliters. For a full 16 US fl oz bottle, that is 473, without a decimal or a unit suffix.
4. Check Time for when you consumed it, then tap Add drink once.
5. Check the resulting drink record before adding anything else. If an entry already exists, edit that record instead of creating a second one.

The Volume field accepts a whole number from 1 to 2,000 mL for one drink entry. Decimal text such as 473.2 is not accepted. The calculator’s larger capacity limit is separate; a result above 2,000 mL does not fit this form. Recheck the portion you actually consumed rather than changing the quantity to get past a limit.

5. Choose the control that fits the amount

Today’s quick Water amount selector uses 50 mL increments from 50 to 2,000 mL. It can select 600 mL, as shown in the real capture, but not 473 mL. Use the numeric Volume field above when the final amount does not match a quick increment.

In the quick selector, Use 600 ml selects that amount and closes the sheet. The separate Add 600 ml action on Today records it. Selecting an amount is not proof that a drink was logged.

Once a real drink is recorded correctly, a favorite can make that same portion easier to reuse. Check the amount each time: a saved full-bottle portion should not stand in for a half-finished bottle.