Let me introduce to you: the IKEA paper tape measure, folded neatly in your wallet.

It's a good exercise in thinking, dhy that is so.

European: "Yes, but not your everyday sources."

1190mm (A0 height) / 841mm (A0 width) ⩰ √2

11" (US letter height) / 8.5" (US letter width) = 1.29411 ...

Countries using the Metric system: 192

Countries using the Imperial system: 3 (U.S., Liberia, Myanmar)

The U.S. rejection of the Metric system can be traced to Thomas Jefferson, who declared it "Too French."

You could have memorized the length of a cheapo Bic pen if that is common in your area; Or a Parker or a Monte-Blanc if you carry one of those.

All recent iPhones (regular models since `03) have a width of 71.5mm. Remember that, and as long as someone near you has an iPhone, you are good to go using it as a ruler. (And people will definitely be, um, impressed).

We have in my kitchen several brands of small forks, all are 19.2mm (just checked. The large forks have a range of sizes). Next time I need to measure something I could just request a fork...

Lol