Forget SI and Imperial and such. Real people use other standards for measurement.
Examples:
distance - laid end to end they would go around the world “N” times.
“It would go from the earth to the moon “N” times”
“it would stretch from New York to Los Angeles”
volume - swimming pools
area - the size of Rhode Island or Texas; football field/soccer field
width of a hair
height - Empire state building
“N” items would fit on the head of a pin
Also the size of a refrigerator, school bus
Of course, the National Weather Service refers to hail the size of golf balls or baseball, or basketball
Fantasy author Fritz Leiber, in his “Fafhrd and the Gray Mouser” stories, always used physical distances such as palm-widths, arms-lengths, stone’s-throws, bowshots, and the like. He measured time in heartbeats (noting the difference between a calm heartbeat and a frenzied one.)
This gave the stories a kind of naturalism, and universalism, and a pre-industrial naivete.
Many years ago, in a live-action role-playing-game, I was “Gnug,” the chief of a small tribe of stone-age people. I gave a particular measurement in “Gnugs.” Someone asked, so I mimed measuring from the ground up to my own height. “One Gnug.”
“The smoot is a nonstandard, humorous unit of length created as part of an MIT fraternity prank. It is named after Oliver R. Smoot, a fraternity pledge to Lambda Chi Alpha, who in October 1958 lay down repeatedly on the Harvard Bridge (between Boston and Cambridge, Massachusetts) so that his fraternity brothers could use his height to measure the length of the bridge.”
I find it amusing that much later Oliver Smoot was chair of the American National Standards Institute (ANSI) and then president of the International Organization for Standardization (ISO).
I walked over that bridge a few months ago in the springtime. The smoot measurements are still there, lovingly repainted every year. Plus various other signs by frats & sororities.
For measuring real people, I prefer non-negative integers. Any other measure – rational numbers, real numbers, negative integers, etc., and you run into serious difficulties: what does it mean to have 1.436 people? Or 1/3rd of a person? Or -27 people? Non-negative integers make it very instinctive and clear to most people.
You can actually buy tiny measuring spoons marked as “tad, dash, pinch, smidgen and drop” (example). Apparently a “tad” is 1/4 teaspoon, and it gets smaller from there.
In places with good public transportation, distances given in subway stops or bus stops. It may even be that the distance isn’t even on an actual route, but “it would be about two subway stops away, if there was a line in that direction”.
Real estate listings in Japan all give walking distance from the closest train station, in minutes. It’s actually defined in law - it’s supposed to be calculated at 80 meter/min (3.0 mph) walking speed, rounded up to the next minute.
Traditionally in Los Angeles all driving distances were given in minutes. e.g. “How far is your commute to work? About 30 minutes. To the beach? 10 minutes.”
I suspect that has declined in popularity as the place has gotten more crowded and the traffic denser and more unpredictable.
Songs, or albums. My workout is timed by songs, my run by albums. A quick round-the-block a couple of times is Rocket To Russia, a decent stretch out is Quadrophenia.