US gallons, UK gallons, liters, milliliters, cups, fluid ounces - volume measurements are a nightmare. And don't get me started on US vs UK fluid ounces, which are different!
Cooking Conversions
Cups to milliliters is probably the most common conversion. 1 US cup is about 237 ml. A UK cup is slightly more. Just use a converter and be done with it!
I keep a volume converter bookmarked specifically for recipe disasters. Has saved many a dinner!