Ask HN: Is there anyone here who still uses slide rules? • Hacker News Board

Re: Ask HN: Is there anyone here who still uses slide rules?

#121

Post by randochatter » Wed, Feb 04, 2026, 4:09 AM UTC

rdiddly wrote: post #84

gcr wrote: post #51

I designed and 3D-printed my own slide rule 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 - most of the fun of the game comes from the mechanics being slightly obscured from the player. S…

You almost have to do this, or buy a used one at a markup, as nobody seems to make them anymore (except circular ones).

[dead]

Re: Ask HN: Is there anyone here who still uses slide rules?

#122

Post by HardwareLust » Wed, Feb 04, 2026, 12:37 PM UTC

kstrauser wrote: post #108

shellback3 wrote: post #106

Earlier quoted context omitted.

Shwllback3 was my radio callsign in Vietnam in '67 & '68.

Nice. I got mine 4 miles off the coast of Mogadishu in '94.

I got mine on the way home from Australia in 1985.

Re: Ask HN: Is there anyone here who still uses slide rules?

#123

Post by sjfloat » Wed, Feb 04, 2026, 4:15 PM UTC

I collect and use them. There are several on my desk right now. There's something about the immediacy that I find very appealing. They don't simply spit out an answer, they display entire relations, which I think is a beneficial intuition.

Re: Ask HN: Is there anyone here who still uses slide rules?

#124

Post by kstrauser » Wed, Feb 04, 2026, 4:38 PM UTC

HardwareLust wrote: post #122

kstrauser wrote: post #108

Earlier quoted context omitted.

Nice. I got mine 4 miles off the coast of Mogadishu in '94.

I got mine on the way home from Australia in 1985.

Did you fly out and then sail home?

Re: Ask HN: Is there anyone here who still uses slide rules?

#125

Post by patterner » Wed, Feb 04, 2026, 10:22 PM UTC

gcr wrote: post #51

I designed and 3D-printed my own slide rule 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 - most of the fun of the game comes from the mechanics being slightly obscured from the player. S…

"cool" is not an Absolute. i think it's extremely cool. like close to εK

Re: Ask HN: Is there anyone here who still uses slide rules?

#126

Post by allanbjorklund » Thu, Feb 05, 2026, 1:17 AM UTC

Yes, I have a few, and I do use them from time to time. I keep one in my daily backpack along with an abacus; mostly just to surprise people when I don't pull out my phone to some more complex calculations that I can't easily do in my head.

Re: Ask HN: Is there anyone here who still uses slide rules?

#127

Post by HardwareLust » Thu, Feb 05, 2026, 1:31 AM UTC

kstrauser wrote: post #124

HardwareLust wrote: post #122

Earlier quoted context omitted.

I got mine on the way home from Australia in 1985.

Did you fly out and then sail home?

Nah, it was the tail end of a WESTPAC, we were on our way home from liberty in Perth. We skipped it on the way down.

Re: Ask HN: Is there anyone here who still uses slide rules?

#128

Post by kstrauser » Thu, Feb 05, 2026, 5:31 AM UTC

HardwareLust wrote: post #127

kstrauser wrote: post #124

Earlier quoted context omitted.

Did you fly out and then sail home?

Nah, it was the tail end of a WESTPAC, we were on our way home from liberty in Perth. We skipped it on the way down.

Similar here! Except we got it going out on WESTPAC, not on our way home from Perth.

Re: Ask HN: Is there anyone here who still uses slide rules?

#129

Post by buddylw » Thu, Feb 05, 2026, 6:48 AM UTC

I have one as a watch bezel that I use in a pinch. Anything you need to scale, divide, or multiply in the real word doesn't need more than 2 significant digits of precision so it works. For example, I've used it to calculate how many grams of coffee will give me a 1:16 to the amount of water/coffee I want.

Re: Ask HN: Is there anyone here who still uses slide rules?

#130

Post by k310 » Thu, Feb 05, 2026, 7:02 AM UTC

I just did so yesterday. I was discussing with the ophthalmologist how to estimate when a very opaque bottle of eye drops was near-empty. (I find this user-hostile)

I've been weighing the bottle on a kitchen scale, and the tare weight is 8 grams, (from the previous bottle) while a full bottle is 23 grams, (from the next bottle) agreeing with the 15 gram (milliliter) stated contents. Assume density of 1.0 g/ml.

So, the fun part was estimating the droplet volume. From the measured rate of decline (7 grams in 40 days) the drop size was 45 microliters. (4 drops per day) Easy slide rule math, but the important thing is that the slide rule requires you to understand orders of magnitude (we had a whole bunch of lessons on this in high school) and units.

The latter two are winners.

Internet lookup only to check results, of course.