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How Slide Rules Work

How Slide Rules Work

4 comments

·November 19, 2025
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clickety_clack

Slide rules are super cool. Such an easy gift to give the engineer in your life.

I never spent the time to get quick with it, but I could absolutely see it being quicker than a calculator. You’d just have to be aware of the limits to its precision if you were in a field that required it.

NetMageSCW

The HP-35 wasn’t programmable- it was just a scientific calculator.

JKCalhoun

Deep dive, for sure. I suspect Cliff Stoll is enjoying this site.

I played with creating a logarithmic slider thing [1] in Javascript that I hoped I could package up as a kind of "widget" people could use on their web pages. But I don't really know Javascript that well—or rather how to make an API out of a Javascript thing.

Anyway, to test it I tried to make an Ohm's Law calculator [2].

I would love to see a site like the one in this post have some kind of interactive slide rule on the web page itself.

[1] https://github.com/EngineersNeedArt/SlideRule

[2] https://www.engineersneedart.com/ohmslaw/index.html (the yellow slider is not directly user-moveable in this example)

kingforaday

This would have been helpful for Sam Cooke.