This Quart to Liter Calculator may help.
Now, a caveat. A "quart of onions" is a volumetric measure where vto actual amount of onions is highly dependent on the physical shape of the onions, i,e, a quart of large chunks will use far less onions than a quart of fine dice.
Conversion from volume to weight is very accurate for liquids and fairly accurate for most solids of a consistent nature, i.e. granulated sugar, long grain rice, as long as care is taken not to compress or aerate.
Now, for your original question:
- 1 U.S. quart (liquid) = 0.946352 L or 946.352 mL
- 1 U.S. quart (dry) = 1.10122 L or 1101.22 mL
- 1 U.K. quart = 1.13652 L or 1136.52 mL
Does that help or are you more confused ??