The formula with 33 substituted
L/100km = 235.214583 ÷ 33 = 7.13
The constant is an exact definition, not a rounded factor: the mile is 1.609344 km, the US gallon is 3.785411784 litres and the imperial gallon is 4.54609 litres. The MPG to L/100km Converter explains where each comes from and gives a longer table.
The same 33 mpg (US) is 39.63 mpg on the imperial gallon, 7.13 L/100km and 14.03 km/L. If your 33 mpg figure came from a British source it already uses the imperial gallon, and the metric answer is 8.56 L/100km instead.
What 33 mpg (US) means in practice
33 mpg (US) is 7.13 L/100km, the combined rating of many compact crossovers with front-wheel drive. This is about the point where a car stops being described as thirsty in American reviews.