I use a similar method but one that takes in slightly more memorization. But the things memorized are good markers to have memorized. And then multiply or divide by 2 the difference between the markers.

For starters 32f is 0c. This most people remember anyway. This gives you a good baseline for winter temperatures.

212f is 100c. This gives a good baseline for a lot of baking temperatures.

98.6f is 37c. This is good for summer temperatures and for human body temperatures.

-40f is -40c. This would be useful in a place that's colder than I want to go to but it's just something I know

Gives slightly better accuracy close to temperature ranges I care about.