Imperial is bullshit; just as stupid as Roman numerals. You have to do math before you even get to the math you want to do.
I've had most of the metric/imperial conversion factors in my head since childhood (having gone to school in a country that started enthusiastically going metric in a fit of pro-EU modernity, then lost motivation half way through and has ever since been stuck inbetween the two, mixing-and-matching both systems, in roughly the same proportion as the Brexit/Remain vote).
I still think of human weight purely in stones and lbs, and human height in feet and inches. Weights of food are in kg and grams, however (if I ever turn to cannibalism, I'll have to convert between the two - fortunately I remember 2.2 lbs in a kilo).
Long distances for travelling purposes are in miles, short distances for furniture and other measurements that aren't people, are in cm and meters. Temperatures are Celsius (Farenheit temps mean nothing to me), power usage is in Watts, energy in joules unless it's about food in which case it's in calories.
My biggest problem with imperial is that I can never, ever remember how many yards there are in a mile.
How the heck does anyone remember the number is 1760? (I just looked it up) What kind of stupid arbitrary number is that?
This is how I used to have to remind myself yards in a mile (pre-internet, when it wasn't easy to look it up),
1 mile = 8/5 km = 100x1000x8/5 cm = (100x1000x8/5)/2.54 inches = (100x1000x8/5)/(2.54*36) yards = 1750 yards
(Though it's actually 1760 yards, because mile to km isn't exactly 8/5).