Convert a measure
One measure in the other system of units, and the tool that pours it. The arithmetic is the site's own - the ounce every recipe is converted with, and the sizes the measures reference prints - so the number here and the number beside a recipe are never two opinions about the same pour.
500 ml is 2 1/8 cups
A measuring jug: pour to the 2 1/8 cups line.
The same sentence appears beside the measure on any recipe printed in Fluid ounces (US), at the number it names.
The sizes the reference prints
The tools themselves →One click from an answer: each size as the measures page writes it, asked in the other system, with the tool that holds it. A size already written in the units you are reading it in is not converted here - a jigger is made to those two sizes, and the reference says what the difference between them is.