Sounds about right the rule of the thumb is roughly times 1.2 UK to US .
Wikipedia
Imperial (UK) gallon is legally defined as 4.54609
litres (~277.42 cu in), which is about 1.2 U.S. liquid gallons. This definition is used in the
United Kingdom, and is based on the volume of 10
pounds of water at 62
°F. (A U.S. liquid gallon weighs about 8.33 pounds at the same temperature.) The Imperial gallon is no longer legal, in the UK, for trade or public administration purposes, but it is used colloquially (and in advertising) for fuel consumption figures in miles per gallon.