Teach me some sliderule skillz

I got a sliderule! (A virtual one on my iPhone.)

It has the following scales: LL/0, L, K, A, B, S, T1, C, D, R1, R2, LL0.

I know how to do multiplication with C and D. I have no idea what all the other ones are for. What neat tricks can I do with this thing?

No idea about using it, but I’d be interested in knowing what the app is called!


I would also be interested in knowing the name of the application.

Further, I have several slide rules of metal, wood, and plastic that I would like to know how to use.

The K scale is for cube roots and cubes. Match it with the D. A 2 on D shows up as 8 on K

A and B are for square roots. Match A with D. It lets you do a series of calculations – sqrt(5) x 7, for instance. For that, you use the hairline to find the square root of 5, then move the B scale’s index (see below) to that number and follow the rules below.

T is for Tangent and S for Sine, I think, but I don’t know how to use it that way.

Using C & D to multiply (for example, 4 X 3). Move the Index (the 1 on the C scale) to 4, then move the hairline slider to 3. If the 3 is off the scale, just move the index on the other side of the C scale to 4 and try again.

Practice using this.

As a former engineering student in the '60s who carried his slide rule with him all of the time, I can tell you the big secret…

It’s a chick magnet.

The nam of the app is (believe it or not) iSliderule.

Ah, I remember using slide rules. I just missed out on having to learn them but I thought they were totally cool. I have a couple of nice antiques in my collection and a cheap Picket I keep in the glove box for calculating mpg (and attracting looks). Anyway, the scales are:

C/D multiplication and division
L is a linear scale (base 10 logs)
A/B are two decade scales (squares and square roots)
K is a three decade scale (cube roots)
S is Sin (and cosine)
T is Tangent (and cotangent)
R is Reciprocal (1/x)

Maybe back then but it takes more effort for the same effect now. You can use an iPhone to connect to a PC via Citrix and control it from the phone. Hum-hum so far right? Have that PC set up so that it can connect to a Mac that runs Unix from the command line and use that to connect to another remote server on another continent that runs a slide rule application and use that to calculate your ETA on your first date. Depending on the hotness of the female, you can add in extra steps to up the awesome factor. Carry a big stick because you will need it to beat them off.

Teach some teens to use it. It’s really eye-opening in terms of making logarithms “click”. It sure did for me, the child of the '80’s.

My high school physics teacher made us learn to use slide rules, because doing so requires you to get good at reading scales, and that’s a valuable skill in science. (I graduated in 1984, and by then, they were obsolete, so trying to buy them was not easy. Most retailers looked at you as if you were nuts if you asked if they stocked them. I was fortunate in that my brother had already been through his class, so I inherited his slide rule.)

They are still used in aviation because of the sight reading. I have one that I bought in the 1990’s. but never learned to use it well. I may try now.

I took out the old ‘family’ slide rule. I’m not looking for explanations. I may have to find a class for this thing. On one side is (parenthesized letters are red on the rule):

   (LL/1)                                       (-0.01<- -0.1)

(e^-x LL/2) (-0.1<- -1.0)
(LL/3) (-1.0<- -10.0)
(T) T
(Sec T) ST
Cos S
LL3 1.0 -> 10.0
e^x LL2 0.1 -> 1.0
LL1 0.01 -> 0.1

On the other side is:

e^x LL0 0.0001 -> 0.01
(e^-x LL/0) (-0.001 <- 0.01)

I can get as much as I need from the explanation you’ve already given. I just wanted to share the fact that I feel slightly boggled looking at it.

If I knew how to use this, would I be able to fly to the moon? Well, except for the lack of propulsion and no oxygen and all.

I think I saw the first virtual slide rule maybe fifteen years ago. Something like this. I thought that using a Pentium computer to rule a slide rule applet was somehow devilishly perverse. So I started using it at work. :slight_smile:

The internet may not have everything, but that is cool. Also, I found the online International Slide Rule Museum. It has a downloadable instruction book for the exact slide rule I outlined above and for many, many other slide rules.



When you see an F (CF, DF) that means the scale has been folded (usually around π). Since so many calculations involve π, it’s just easier to have a scale that begins and ends with π.

When you seen an I (CI, DI, DIF) that means that the scale has been inverted and is useful for simplifying division.

I’m the sort of nerd that needs to know how everything works, every scale on the slide rule, every button on the calculator, etc. I’m a lot of fun at parties.

One advantage of a circular slide rule is that you never have to try again. You also don’t need any xF scales…all the scales are already folded around any number you might choose.

Circular slide rules are (well, were) the norm in aviation, and appear to have been popular with Russian engineers, but they don’t seem to have caught on among american engineers. I have a Concise brand one that was a promotional giveaway from the Johnston Pump Co. of Glendora, CA. It has only A,K,C,D, and CI scales. The back is printed with a number of conversion factors and formulas.

My HS physics teacher did, too, although I’m about 10 years older than you.

Remember to keep everything in scientific notation, because the slide rule isn’t going to do that for you.