On my job I use some equipment that is calibrated to the "RF Engineer" standard of 0 dB equals one milliwatt in 50 ohms. But other gear is calibrated to the CATV standard of 0 dB equals 1 milliVOLT in 75 ohms.
I could never remember how to get back and forth until I tried some calculations using 63 ohms as a compromise impedance.
Then I found that the RF Engineer standard is about 1/4 of one volt. That's something I can remember. And that the difference between the scales is 48 dB. Four dozen is another number I can remember. And now you can remember, too.