# Who can use a slide rule? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [May 31, 2002, 5:46am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693 "2002-05-31T05:46:52Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Rilchiam](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@Rilchiam](https://boards.straightdope.com/u/Rilchiam)\ **Post date:** [May 31, 2002, 5:46am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/1 "2002-05-31T05:46:52Z")
Or knows someone who can? My dad can. He’s 74. He says it’s an anachronism now. [hijacking own post]I’ve got a tune running through my head. “Who can use a slide rule/Sprinkle it with dew…”[/hijacking own post] ---
**Author:** ![j666](https://avatars.discourse-cdn.com/v4/letter/j/9de0a6/32.png) [@j666](https://boards.straightdope.com/u/j666)\ **Post date:** [May 31, 2002, 5:51am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/2 "2002-05-31T05:51:41Z")
I’ve always wanted to know how to use a slide rule; it has to do with adding with logs do to multiplication, right? ---
**Author:** ![heresiarch](https://avatars.discourse-cdn.com/v4/letter/h/278dde/32.png) [@heresiarch](https://boards.straightdope.com/u/heresiarch)\ **Post date:** [May 31, 2002, 6:21am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/3 "2002-05-31T06:21:14Z")
I can do the basics. Yes, multiplication and division are done by adding and subtracting logs. My dad gave me a pretty fancy one with a total of 18 different scales on it. Scales for square and cube roots, etc. I’m not sure how you deal with more than three significant digits. I believe that you have to break the problem into sub-problems and add the intermediate results. Here’s a simple example, 18 \* 33 ```auto fixed scale: 1............2.......3.....4...5...6..7. slide: 1.............2.......3.....4. ^ ^ A B ``` A) Line up the index (one) on the slide under “1.8” for 18 B) Move the hairline over the “33” on the slide scale and read the number above it on the fixed scale. It’s 5.9something. You know that the answer has to be close to 600 (20_30). You know the last digit has got to be 4 (because 8_3=24), so the answer is 594. ---
**Author:** ![WillGolfForFood](https://avatars.discourse-cdn.com/v4/letter/w/82dd89/32.png) [@WillGolfForFood](https://boards.straightdope.com/u/WillGolfForFood)\ **Post date:** [May 31, 2002, 6:33am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/4 "2002-05-31T06:33:21Z")
Boy, am I getting old. When I was a freshman engineering student, one of the biggest decisions we had to make was whether to buy a K&H or Decilon slide rule. (Those were the two largest makers of slide rules - sort of like Ford and General Motors.) ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [May 31, 2002, 7:16am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/5 "2002-05-31T07:16:03Z")
I used to have one, courtesy of my late grandfather, an army engineer. I remember the basic arithmetic, but these days I’m much more likely to grab for the nearest calculator, or pencil and paper. ---
**Author:** ![Tortuga](https://avatars.discourse-cdn.com/v4/letter/t/c4cdca/32.png) [@Tortuga](https://boards.straightdope.com/u/Tortuga)\ **Post date:** [May 31, 2002, 7:30am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/6 "2002-05-31T07:30:54Z")
“Pookie!!!” Wasn’t that the slide rule of Bill Gates in Berke Breathed’s Bloom County/Outland’s _Citizen Kane_ spoof? Which I can never think of without thinking about “hairy fishnuts” (hari krishnas). ---
**Author:** ![kambuckta](https://avatars.discourse-cdn.com/v4/letter/k/53a042/32.png) [@kambuckta](https://boards.straightdope.com/u/kambuckta)\ **Post date:** [May 31, 2002, 7:38am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/7 "2002-05-31T07:38:16Z")
I remember trying desperately to figure out what a slide rule was for back in Yr 7 (1972 FYI) and decided that I was NOT the kind of kid who was going to excel in maths or the sciences. They were cool for ruling-up pretty margins on my lit. essays though, until I realized that _pretty_ was not cool either. I still don’t know what to do with a slide-rule. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [May 31, 2002, 7:58am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/8 "2002-05-31T07:58:20Z")
> [@](#): > > \*Originally posted by j66 \* > \*\*I’ve always wanted to know how to use a slide rule; it has to do with adding with logs do to multiplication, right? \*\* This site [Slide rule basics](http://www.hpmuseum.org/sliderul.htm) is pretty good. ---
**Author:** ![Rilchiam](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@Rilchiam](https://boards.straightdope.com/u/Rilchiam)\ **Post date:** [May 31, 2002, 11:46am UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/9 "2002-05-31T11:46:17Z")
**heresiarch** : Impressive! **WGFF** : Hey, I still remember turntables, if it’s any consolation. **Tortuga** : “Ookie”. ---
**Author:** ![flyboy](https://avatars.discourse-cdn.com/v4/letter/f/4da419/32.png) [@flyboy](https://boards.straightdope.com/u/flyboy)\ **Post date:** [May 31, 2002, 12:06pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/10 "2002-05-31T12:06:47Z")
I use a “whiz” wheel (circular slide rule) all the time for flying. You can see what I’m talking about [here](http://www.sportys.com/acb/showdetl.cfm?&User_ID=953633&St=1350&St2=-57177602&St3=-60284000&DS_ID=2&Product_ID=1200&DID=19). The Navy gives us a similar but smaller wheel. ---
**Author:** ![Knighted\_Vorpal\_Sword](https://avatars.discourse-cdn.com/v4/letter/k/ac91a4/32.png) [@Knighted\_Vorpal\_Sword](https://boards.straightdope.com/u/Knighted_Vorpal_Sword)\ **Post date:** [May 31, 2002, 12:39pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/11 "2002-05-31T12:39:26Z")
When I was a teenager in the 1970’s, I went out and bought a slide rule. Then I went to the library, and took out a book that told me how to use it. I got pretty good at it - good enough to use it in chemistry instead of a calculator. Unfortunately, it’s long gone. Are there any places that still sell them? ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [May 31, 2002, 1:03pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/12 "2002-05-31T13:03:09Z")
I still have my old slide rule; it actually was my cousin’s and probably dates from the 50s. I take it out from time to time to see if I still remember. I can multiply and divide and find square and cube roots. I don’t believe anyone makes them any more. No market. Calculators are superior and fairly cheap. ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [May 31, 2002, 1:06pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/13 "2002-05-31T13:06:48Z")
BTW, if you want to try one out, go to [Virtual Slide Rule](http://www.taswegian.com/SRTP/javaslide/javaslide.html) ---
**Author:** ![TV\_time](https://avatars.discourse-cdn.com/v4/letter/t/f17d59/32.png) [@TV\_time](https://boards.straightdope.com/u/TV_time)\ **Post date:** [May 31, 2002, 2:17pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/14 "2002-05-31T14:17:48Z")
After reading the above posts this morning, I went looking for my old slide rule and found it in the bottom of a closet and fooled around with it for a while proving to myself that I still could use it. When my wife came downstairs to say hi, I proudly stated, “I’ve been playing with my slide rule.” She looked at me, pointed at my groin area and said barely holding back a smirk, “Is that what you’re calling ‘it’ now?” and broke up laughing. Once again I manage to put my foot in my mouth. Too bad we don’t have a preview function with our mouths. TV ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [May 31, 2002, 5:53pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/15 "2002-05-31T17:53:45Z")
Anybody old enough could have used them, but the real slide rule uber-geek question is: Can you still make a good argument for your side in the steel vs. wood (bamboo) debate? (No one ever argued for plastic of course.) ---
**Author:** ![Smashed\_Ice\_Cream](https://avatars.discourse-cdn.com/v4/letter/s/ed8c4c/32.png) [@Smashed\_Ice\_Cream](https://boards.straightdope.com/u/Smashed_Ice_Cream)\ **Post date:** [May 31, 2002, 6:36pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/16 "2002-05-31T18:36:08Z")
I decided that I wanted to learn how to use one about 8 years ago, but I think I only know the very basics still. I’m WAY too young to really have had a chance to learn when I was younger (I’m 29 now, I had a scientific calculator in 5th grade) **RealityChuck** , that’s so cool! SOmehow the ‘modern technology to make a slide rule’ thing sticks in my head funny. ---
**Author:** ![WillGolfForFood](https://avatars.discourse-cdn.com/v4/letter/w/82dd89/32.png) [@WillGolfForFood](https://boards.straightdope.com/u/WillGolfForFood)\ **Post date:** [May 31, 2002, 6:51pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/17 "2002-05-31T18:51:47Z")
> [@](#): > > Can you still make a good argument for your side in the steel vs. wood (bamboo) debate? I dimly remember some discussions along those lines, although the age of plastics may have already taken over before I got involved with these things. I sort of remember my slide rule as being made of wood, but I don’t recall having much of a choice in the matter - I bought my slide rule at the campus bookstore (as did most of the other engineering stuents). IIRC, the argument against steel was that it was affected by temperature changes (but wouldn’t both sections of the slide rule be affected equally?) and the argument against wood was that it could warp. The best thing about slide rules, of course, was the really neat belt-looped case that you got to put it in and walk around with. They all tried to hide it of course, but you just knew that those English majors were green with envy. ---
**Author:** ![amarinth](https://avatars.discourse-cdn.com/v4/letter/a/3be4f8/32.png) [@amarinth](https://boards.straightdope.com/u/amarinth)\ **Post date:** [May 31, 2002, 6:54pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/18 "2002-05-31T18:54:04Z")
I used one once, but I don’t actually know how to do it… But I can use an abacus. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [May 31, 2002, 8:34pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/19 "2002-05-31T20:34:41Z")
I learned how to use a slide rule in High School, and got pretty goo at it. I was faster than the guy who had the (still pretty primitive) calculator, especially at square roots and trig functions (only the HP-35 would do those – and it cost $395). Just before I went to college, I found $20 in the road, and used it to buy a Pickett’s slide rule with all the scales, a leather case, and an inscribed monogram plate. I’ve still got it, along with a lot of other slide rules I’ve bought over the years at garage sales and elsewhere. I used a slide rule for my first two years at MIT, finally giving it up because a.) courses started demanding four-place accuracy (which your standard slide rule wont give) and b.) because the HP-25 came out at a affordable $195. I intend to teach my daughter how to use one of these. There was a very good essay in the Amercan Heritage Magazine o SCience and Invention several years ago, comparing the use f a slide rule vs. calculators as the use of a drawhorse vs. power tools. The first case requires artistry and knowledge, while the latter is programmed and without intuition. There’s some sense in that. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [May 31, 2002, 8:40pm UTC](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693/20 "2002-05-31T20:40:22Z")
Don’t know much about geography Don’t know much trigonometry Don’t know much about algebra I don’t know what a slide rule is for [Next page](https://boards.straightdope.com/t/who-can-use-a-slide-rule/111693.md?page=2)