[robbrown451]

You should check out google images for piano key clip art. Almost all of them get it wrong. They assume a black key is centered between two white keys, but that is only true for g#.

The width of all keys, white or black, should be equal to one another at the back of the keyboard.

The width of the white keys should be exactly equal to one another at the front of the keyboard.

Those can't both be true (since 5/12 isn't equal to 3/7), so the former has to be fudged a bit.

My formula is in a different comment. :)

[userbinator]

For some reason, this reminds me of "What happens when you ask people to draw a bike": https://news.ycombinator.com/item?id=17699017

The black and white keys are instantly recognisable as a piano, but need a bit more inspection to notice the error.

[robbrown451]

Interesting. Some people got the bike right. I'm quite sure I can draw a proper bike, but I have a long history in drafting and mechanical design.