A US liquid cup is different from a nutrition-labeling cup

NIST’s conversion table lists a US cup as approximately 236.5882 mL. Moyoutil uses a factor of 236.5882365 mL for its US liquid cup. In contrast, the FDA’s household-measures guidance defines a cup as 240 mL for nutrition labeling. Treating 240 as the precise conversion of every US cup mixes two conventions.

The actual function converts 0.5 cup to 118.29411825 mL and 2 cups to 473.176473 mL. Two cups under the 240 mL labeling convention equal 480 mL: a difference of 6.823527 mL. This is a calculated difference between conventions, not a measurement error or a recipe failure rate. In the code below, unit is the current tool’s conversion function.

const unit = convertUnit;
unit("volume", 0.5, "cup", "mL") // 118.29411825
unit("volume", 2, "cup", "mL")   // 473.176473
2 * 240                          // 480
Number((480 - 473.176473).toFixed(6)) // 6.823527
Two US liquid cups equal 473.176473 mL; two FDA nutrition-labeling cups equal 480 mL
An original diagram calculated from the two conventions. FDA refers only to nutrition-labeling purposes here. Shape areas do not represent volume ratios.

NIST SP 811: cup, ounce and fluid ounce · FDA: household measures for nutrition labeling

oz measures mass; fl oz measures volume

NIST lists grams per avoirdupois ounce separately from milliliters per US fluid ounce. In Moyoutil, 8 oz converts to 226.796185 g, while 8 US fl oz converts to 236.5882365 mL. The same number 8 describes different quantities. The tool takes no ingredient or density input, so it does not convert cups to grams.

unit("weight", 8, "oz", "g")    // 226.796185
unit("volume", 8, "floz", "mL") // 236.5882365

Choose Volume in the unit converter, select US liquid cup as the input unit, and choose mL for the output. Enter 0.5 for half a cup. If the source explicitly specifies a 240 mL cup, use its stated mL value rather than this tool’s cup option. The tool uses US liquid measures; it has no separate options for Imperial measures or nutrition-labeling cups.

Frequently Asked Questions

Do the displayed decimal places indicate measuring accuracy?

No. The interface displays up to eight decimal places. That is a display setting, not a guarantee about measuring-cup markings or real measurement accuracy. Check the source’s unit convention and round for your final use.