Do You Remember the Slide Rule?

It wasn’t all that long ago that engineers, astronauts, mathematicians, and students proudly carried the original pocket calculator. I had one and thought I was proficient at it. Sadly, I misplaced it years ago.

The slide rule was a simple device with one sliding part that could do complex mathematical calculations in moments. Multiplication, division, roots, logarithms, and even trigonometry could be performed with ease. But as technology marched forward with sophisticated computers and graphing pocket calculators, the lowly slide rule was forgotten.

Much of the engineering of the world we live in was designed with the use of slide rules, and yet they are almost forgotten today. Do you have a teen-aged child or grandchild? If so, ask him or her what a slide rule is. I suspect he or she won’t know.

Wikipedia states that William Oughtred and others developed the slide rule in the 17th century, based on the emerging work on logarithms by John Napier. The online encyclopedia then goes on at length to describe the history, use of, and eventual obsolescence of the slide rule. You can read the article at

Want to amaze your grandchildren? Buy a slide rule to show them. You can also keep it for nostalgia reasons. Slide rules can still be purchased from a number of vendors for about $20 or so if you start at

No batteries required.


I’ve got two or three; I used them in engineering school. You can guess when that was. One of them was my dad’s…

    My dad also had one from his college days after WWII. He gave to me when I started my chemistry degree in the late 60s. I still have it, in its nice leather case. My sons know what a slide rule is, but have never used one – it was graphing calculators for everyone when they were in high school.

I’ve still got mine. I wanted one in high school and bought one before university. About two years later, the first HP calculators came out. One friend at university bought one for $300. I waited two years until they were down to $30.

… actually, now I remember that my sister bought me the slide rule as a present for university.

I have one from my 9th grade Algebra class…ca.1959 .It is still in the original box too. Me? I don’t recall how to use it:)

My husband is the proud possessor of his, which he has had since school days (6th form in 1957, he tells me). personally, I wouldn’t have the foggiest idea how to use it – I never got past 5th form maths.


I still have mine. We weren’t allowed to use calculators in exams.

I guess I will jump in as well, I to have the Pictured slide rule plus two others thanks to the G.I. Bill when I attended College. I was also studying Electrical Engineering . I helped replace these slide rule’s with Computers..

$20? The POST Versalog slide rule I bought in 1956 in school was more than $20. The big issue for students was whether or not they could use the slide rule during an exam. Later, a few coworkers had a K&E slide rule that was 24″ long.

I still have mine and also my dad’s. I can still remember using mine down at Ohio State during an exam, but didn’t continue that much beyond my freshman year. My dad was an organic chemistry major there.

I bought one many years ago, and never learned to use it. :(

Still have my first one – a Faber Castell model – used in year 11 and 12 for Maths and Physics classes and during my Science degree. Didn’t own a calculator until after I started teaching!

Actually, two sliding parts.

While today’s college student have to bring a laptop I was required to bring a slide rule and an axe for Forestry school. The slide rule was a Log Log Duplex Decitrig and the axe was Plumb. I still have both after almost 60 years.

Actually, two sliding parts. I had (still have) a 6″ high quality model. Never could see carrying around one of those 12″ models in a holster hanging from the belt, as others in engineering school did.

This brings back memories of 1955 at Valpo Tech when every student had a Post or K&E strapped to their belt. Thanks Dick for bringing back.

I also remember using the slide rule in high school. I didn’t use it in college, as I transferred from engineering to accounting. I also had a 3 inch thick book of mathematical tables in high school, which carried the answers to two dimensional calcs (row and column presentations) to eight digits. The slide rule couldn’t get answers to eight digits, but could check the answer or give a quick answer. After graduating from high school, I also then remember mastering the ten key adding machine, the remains of which can still be found on the right side of many computer keyboards. Even today, mastering that ten key pad, without looking, with hours and hours of practice, is advisable for accountants. After leaving school, I remember being an auditor in businesses that used a paperless calculator that, as I recall, had nine digits down and nine digits across. There were “clear”, “plus” and “minus” keys. The cumulative answer of a long list of entries was shown at the top of the machine. As I recall, two operators would add up stacks of documents and see if they got the same answer – since the machines were paperless, that was the only way to know if the operator had made a mistake. I don’t remember the name for those machines right now.

I have never used one, but my mother a proud “Rosie the Riveter” held onto and used hers for YEARS. My husband, an electrical engineer, kind of remembers how to use his. And our 19 year old son, an electrical engineer and curious soul, asked a neighbor how to use one.

At the U of Minn. a student wrote a derogatory letter in the school news paper about engineering students. When someone found out he had dropped out of engineering he posted an apology to all engineering students except those who wore a slide rule on their belt.

The machine that Ris Taylor speaks of was a “Comptometer” and I became a expert on it, but never learnt to type. In later years I used a slide rule but as a surveyor we more frequently used logarithms for accuracy. My first “calculator” was actually an old Fawcett machine that did multiplication and division of seven or eight digit numbers.

I still remember the day my Dad took me downtown to purchase my very own Keufel and Esser slide rule. I still have it, plus a couple of my Dad’s, including a 6″ one and a 15″ one.

The slide rule? Yeah, I remember it: No more than 20 words on a single slide. I used the other kind my freshman year at Carnegie Tech. HPs first four-banger (+-x/) came out my sophomore year…”only” 99 bucks. My dad used a 20-inch log-log slipstick at MIT in the 40s.

I had a huge slide rule that hung from the top of a chalkboard, and I taught my math students to use a slide rule. One parent was so impressed that he gave us a classroom set of slide rules, which made it much easier. The kids loved it and felt awfully smart! They were only in seventh grade, after all.

    My high school chemistry teacher had one of those huge ones atop the chalkboard (1966). Never imagined I would be using one myself until entered that first college chemistry class and it was required! Don’t think I could make sense of it today though. Glad to have my hand held calculator instead.

I had my dad’s slide rule (he was a civil engineer) until my younger son, now in his late 30s, decided he would like to have it so I put it in his Christmas stocking a year or so ago. I don’t know if he knows how to use it but I do know he treasurers it.

Brings back bad memories of Trigonometry class senior year high school. Decided that my future was in words, not numbers. Irony,I must now review budgets & the books…

    Ahhhhhh, yes. Try adding up that column of numbers in the ledger with the slide rule. ‘-)

On a closely-related topic, when I was a Junior in high school in 1969-70, we were probably one of the very last classes to learn to use five-place logarithm tables with proportional parts. We would buy a discounted year-old CRC Handbook of Chemistry and Physics for the log tables.

    OMIGOD! At the sound of “five-place logarithm tables with proportional parts” I experienced an instant abdominal sensation of pending reverse peristalsis. Where are my Tums?

    Scott I have an old copy of Shortrede’s 8 place table of logarithms I can let you have real cheap :-)


I still have my three, a six inch and twelve inch, both plastic models, and a twelve inch metal one that was plastic coated and spring loaded with adjustment screws to make sure it all stayed aligned correctly. Got it while I was in high school back in the mid 60′s. Replaced it in the mid 70′s with a German made Adler (I think) scientific calculator, cost about $100 dollars at the Fleet Exchange in Hong Kong but was worth several times that amount. That calculator and next four or five I owned all died, but I still have the slide rules. Sometimes “old” is better.

I still have the circular calculator I used when I learned to fly a plane for navigation. Same thing, different shape.

That little device engineered most of the technology and vehicles used to land humans upon the moon.
Modern computers have not been able to repeat that feat.

I still have about 10 of ‘um. One is a circular one that was used in chem. class. Vertical curves are still easier to compute with a slide rule. The SR-71 was designed by Johnston with one. I still have and use a Curta II that I use during formula 1 races to convert kilometers to mph and calibers in metrics to caliber of pistol and rifle bullets. The Castiel/Faber has an adding/subtracting slider on the back. Neat gadgets to play with.

    The story about Kelly Johnson designing the SR-71 with a slide rule is a popular myth. Yes, hand calculators were not available at the time, but the IBM 704 that the Skunk Words used was.

Check out your slide rule here:
Mine appears to be worth about $130.

Fond memories. I first learned to use a slide rule sixty years ago as a freshman engineering student. We had a one hour per week class dedicated to slide rule usage. The best then were K & E with Post a close second. They were made of bamboo. I was an NROTC student and the government would only buy us the plastic version which worked very well. Except in the Mid-west winter when the movable slide portion would shrink and become very loose when exposed to cold weather walking to class.
The challenge in using the slide rule was keeping track of the decimal point. A set of rules applied and if the slide extended to the left the decimal point moved one place. The accuracy was adequate for most engineering applications.
By the time I finished four years of college and three years in the Navy the calculator was coming on the scene although the early ones were expensive — $300 in 1960s dollars.
Thanks Dick for bringing up the subject.
Dave, retired Electrical Engineer

On June 14th 2014, I presented my grandson with my slide rule from my college days. I had mounted it in a box, under glass, with the notation ‘In Case of Power Failure – Break Glass’. On the back of the box I pasted a letter to him asking him to pass it on to his son. He graduated from UCSB as an mechanical engineer. It was a sneeky way for me to send my note, and signature, down the family line.
The slide rule is a Picket & Eckel model N4-ES Log Log vector yperbolic
dual base speed rule
Roger Root

I got my first slide rule when I started teaching, 60 years ago. We didn’t even have calculators, then. There were adding machines, but they wouldn’t multiply or divide. I used my to average the grades of my students. I still have it. Mine was made of wood and cost about $15.00 which was a lot of money then.

I still have mine in the leather case, one of my Dad’s and my circular slide rules. When I taught High School, we had the huge one over the blackboard, and a transparency slide rule, that we projected onto a screen to teach the students to use a slide rule. They complained vigorously.

I think I was a junior in College when the TI calculator (4 banger) dropped from $200 to $125 and I bought one. I don’t remember the $300 price.

Went on a steam train excursion with the family three years ago, in rural Alberta. The stopover point was Great Valley, where we got off to wander the town and have a meal. Dropping into their local museum, it was amusing to see the old telephones, clocks and farm impliments. To my horror, my old slide rule was on disply behind a glass counter! I have now aged to the point of joining my parents in being obsolete. This hurts.

There’s quite a trade in slide rules – people will collect most anything. I have about 100. Perhaps my favourite is one from WWI designed to calculate the correct elevation of a field gun. My grandfather was in the Marine Artillery handling a howitzer (known as “Granny”) during WWI but he never mentioned using a slide rule or similar equipment. Shame – it would have been good to have something come “full circle”.

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