I recently found out Shigeru Miyamoto (the creator of Mario and Zelda) likes to carry a tape measure around with him, guess how big things are, and measure them to check how close he was
I've started doing the same thing and it's a lot of fun 📏
I did the reverse. I went into the hardware store to buy some chain. As it has to be cut, it is not self-service, I told the Lady that I need this much chain and held my hands apart, and added "50cm". She said "Hold it", took her tape, and measured the distance between my palms. It was exactly 50cm.
Same at the butchers. "I take that piece, it should be 800g." Scale: 802g