Naw. I used to, but it's so long ago, I'm not sure I could do it now if you put one in front of me. What you don't use atrophies.

Yes. Still use my E6B, no matter how much hate I get from other pilots.

I still use one of mine on occasion. I would say 2-6 times a month.

Yeah, to intimidate kids when they don't deliver academically :)

I have two or three that I inherited from my dad. I've never learned to use them because I haven't thought of something I'd use them for. The one thing I could think of is quickly doing fractional math while woodworking (what width will I have if I rip this 7.5" board into 4 pieces?) but in reality I just don't actually do that much math while woodworking.

Now that's a properly dead skill, surely. I have my dad's one somewhere, and know roughly how it works, but I've not touched it this century.

I also have one of these: https://archive.org/details/spencersdecimalr0000unse ; I believe they were popular around the time of the UK converting to decimal currency, to save people having to do the transitional arithmetic. Had a bunch of other tables in. A physical LUT.

I wonder if there's anyone with abacus skills here. I hear that held out against calculators a lot longer, for shopkeeper uses.

I do not use, and have never used, a slide rule. My grandfather was an aeronautical engineering / materials scientist for McDonnell Aircraft, and did a lot of foundational work on heat shields for early space flight (or so I am told). He was eventually named a McDonnell Douglas Fellow, back when there were fewer than 15 Fellows - the company, at the time, took out a full-page ad in Aerospace Magazine announcing it.

I have his slide rule, that he used for ages. It's a mystery in a box to me - I have not the foggiest clue how it is used - but I cherish it.

I did a little nostalgia threat on Mastodon recently. The sixth picture is of the slide rule I took to High School in 1973.

https://social.bau-ha.us/@raganwald/115979168665997624

Although slide rules are a "dead skill," Aviators typically learn to use something called an E6B Flight Computer, which works on the same principle as a round slide rule.

https://pilotinstitute.com/e6b-made-easy/

I have one in my flight bag and was required to demonstrate proficiency in its use. Of course we fly with connected digital devices these days, but having an analogue backup that operates even if the power fails is important.

Knew a mechanical engineer at a place where I interned. Asked him about it and he joked that he didn't trust those transistors before explaining that it's just muscle memory to him and while a calculator would be faster he'd still earn the same per hour. Apparently I was the first to ask him in over a decade as everyone had moved on to do stuff in software and no one was pushing him to use a calculator anymore. Interns didn't inquire because they thought it must be some esoteric/religious practice. Last I heard he was still working there, management asked him to stay on past retirement age for his invaluable skillset. While its probably some other skill I just like to imagine the suits in a meeting where they decided to keep him on for this particular "skill" that no one else in the company had anymore.

Besides Cliff Stoll? ;-)

Not in a few years, but now that you've reminded me, I should pick the habit back up.

Seen yesterday on someone's blog

[You Need A Kitchen Slide Rule](https://entropicthoughts.com/kitchen-slide-rule)

When I was in high school, (early 1990s,) there was a giant one mounted above the blackboard. It was clearly used for instruction in the past, but it looked so cool that no one wanted to remove it.

Every once in awhile a teacher would spend about 10-15 minutes showing how to use it. Everyone would "oooh" and "awww" and then we would all laugh about how we didn't need to use them now that we all had calculators in our pocket that were more powerful than the computers that put people on the moon.

It's always nice to learn about the past so we can appreciate what we have now.

Yep. I have one and I keep showing off how to do math using it, to kids.I have also replaced the broken slider with a plastic piece after etching the log scale onto it.

You mean like this one:

https://www.flickr.com/photos/jonsphotos/218609214/

My father is an electrical engineer and uses one

I used them in high school in the late 1990s... just to get an extra challenge. I had my dad's and grandfather's and I picked up a couple at garage sales. I still have a collection, but haven't really used them in years. I'll probably break them out again when my kids get in middle school / high school math for fun. They are great for learning the rules of logs.

A big 6-foot K&E sliderule hung at the front of my high-school chemistry classroom, but was never used. At graduation ('91) I asked the teacher if I could have the slide rule and she said "sure".

I keep it now in my office, and once a year I bring to the data visualization class I teach at UChicago, to show how it works, and to show it as an example of a visual device in aid of computational thinking (nomographs being another great example).

Related (60 comments, How slide rules work)

https://news.ycombinator.com/item?id=45985196

I bought a vintage (pre-WW1) circular slide rule. But it's too much of an "artifact" to use - I'm afraid I'd damage it.

We learned to use them in high school (in Canada) in the mid-late '70s. Electronic calculators were just becoming widespread, and not everyone had them.

I think I can do basic calculations with them, although I really haven't touched one in many years.

Yeah. Pickett N600-ES. Sometimes I will solve a problem with it just because I can. Keeps the mental model fresh. Mostly just use an HP 42s though.

I will note I didn't get it or use it until about 1998.

I have a little collection of slide rules. I love those things.

I'm not old enough to have used them to do calculations, but I find them extremely useful to explain logarithms and how multiplication can be represented by the sum of logarithms. I actually work with grad students who should know these things, but watching it in a slide rule on their hands really helps to build intuition.

I own my grandfather's slide rule, he was a master toolmaker for Rolls Royce (aerospace engines) in North London during WW2.

I bought one a few months ago off of ebay after I realized how important logarithms are in many different domains (including machine learning & information theory)

I've acquired one for curiosity (a relative used to teach engineering, he was thrilled I wanted one, gave me his own)

I used it a few times, it works, of course, ... but it's not fast and not precise so I don't think anybody would use it to be productive in 2026

It sits in a box

I used a slide rule for some of my high school physics tests in the 2010s, just for fun. I lost a few points from messing up order of magnitude calculations, but it was totally worth it. I've since collected a few more slide rules from estate sales in my neighborhood. I wish more people knew about them—they're such a neat and elegant part of engineering history, which is why I keep them around.

I have no use for them on a day-to-day basis, though. An abacus is more useful for things like counting board game points and adding up taxes.

I have half a dozen of them (including my father's from college) that I cherish, but do not use. I love the simplicity and elegance of the design. (Slide rules do a lot with operations that essentially boil down to addition, subtraction, and looking up function values in tables.)

I have some from my father, but even though he showed me how to use them a long time ago, I never actually used them. I do however encourage anyone with an interest to go to the Arithmeum in Bonn (Germany) if you have the chance. It houses an large collection of regular and specialized sliderules as well as other (mechanical) computational devices.

https://www.arithmeum.uni-bonn.de/en/arithmeum.html

I have one on my watch. It’s a citizen with a circular slide rule /E6B flight computer. I need my reading glasses to use it, but it’s fun.

It can reliably get me 2 sig figs, and a decent guess at a third. But… if I think about it for a minute, I can usually get that in my head anyway. Being able to setup a ratio is great though for unit conversions and things.

It’s also really good for answering that question when driving where you’re like, ok if I go 10mph faster how much sooner will I get there which is otherwise hard to do mentally.

Most of the benefit of using a slide rule in my experience comes not from using it, but from thinking LIKE you’re going to use a slide rule. You learn to freely use scientific notation with ease, and mental estimation to get the order of magnitude right.

And just my 2 cents, but circular slide rules are where it’s at.

Yes, but just as a ruler. It belonged to my Dad who was an avionics engineer starting back in the 1950s. He worked all over the world seeing out the end of the British Empire. It smells of old cigarettes and is very worn and chipped.

I was not allowed to use a calculator in my high school calculus class but I was permitted to (and did) use a slide rule.

I designed and 3D-printed my own to help me play Balatro!

Balatro is a roguelike survival game where you need to multiply "chips" and "mult" together to meet a requirement each round. You get three chances to draft enough resources to survive. I designed my own slide rule to help with the mental multiplication.

Since I designed this slide rule myself, I was able to make a couple unconventional design choices that fit my needs better than an ordinary ruler-type. For instance, mine has three octaves so it can represent numbers in the ones, thousands, or millions' range, for example; no need to track arbitrary powers of ten. Since it's a rotary rule, it wraps around; you can compute quantities beyond the range - 353×24 shows on the device as 8.24, so you can think of it as 8.24 thousand, for example.

Holding a physical object in my hands while playing helps more than I thought it would. Should I take a card that increases chips by 600 or increases mult by 1.3×? Do I need to take a card to clear the blind in the short term, or do I have enough resources to take a slower card that will scale better over time? Even just looking at whether the marks are more densely packed on the "Chips" side vs the "Mult" side of the device gives a visceral, physical sense of what my build needs to focus on.

Pictures and .STL: https://www.printables.com/model/1026662-jimbos-rotary-slide...

Github repository: https://github.com/gcr/balatro-slide-rule

The actual plotting code used Marimo notebooks, which host a python in your browser via WASM. Take a look here: https://marimo.app/l/4i15d7

In 1995 I used slide rules in Fort Sill, Ok. Haven't used them since.

I built my own slide rule in school for fun! It looked pretty cool to me at the time. The template is still out there if you search something like "paper slide rule".

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