The US liquid quart is a US customary unit of volume. NIST lists it as 0.9463529 liters. It is one quarter of a US gallon, so four quarts fill a gallon, and it holds 2 pints, 4 cups or 32 fluid ounces.
Conversion
qt = gal × 4
fl oz = qt × 32
L = qt × 0.9463529
Example
Half a gallon is 2 quarts, or 64 fl oz. Three quarts are 3 × 0.9463529 = 2.839 L. The chart in how many ounces in a gallon lists the quart beside the pint, cup and gallon, and quarts to liters converts any value.
Common mistakes
A quart is not a quarter of a liter: it is 0.946 L, about 5% less than a liter, so a liter bottle holds slightly more than a quart.