Digital Slide Rule 4+

Ace Hoffman

Designed for iPad

    • 5.0 • 10 Ratings
    • Free



Four different types of slide rules with dozens of scales plus working models of historic slides

The slide rule was used for over 400 years as a calculating/estimation tool. Abandoned with the advent of hand-held calculators, computers and smart phones, their elegant simplicity is still a thing of wonderment. This program replicates the most common types of slide rules: Straight, circular, spiral and cylindrical. Dozens of scales are included and numerous features that could never exist on a physical slide rule are also included, such as color options, numeric displays of the values under the hairlines, and so on.
Slide rules were used to go to the moon and to build bridges, skyscrapers, tunnels, aqueducts and nearly everything else. Slide rules were simple to use and accurate enough for most occasions.

Also, note that this program is processor-intensive and with heavy use, will probably drain your battery quickly. Every effort has been make the program efficient, but nevertheless, some functions take a few moments to occur, including initial load, which can take three or four seconds, or perhaps a little longer. Nearly 30,000 "nibs" are created during this time, as well as over 3,000 labels, so please be a little patient! Because of all the detail, it looks best and runs best on a large-format machine such as a tablet. Also because of all the detail, the 30-loop spiral slide rule converts to a low-rez "bitmap data image" while you move it, then back to a "vector based image" as soon as you release.

Includes a brief side show slide show of famous and interesting slide rules, most of which are in the author's collection. Two are public-domain photographs of antique slide rules.


Notes on usage: Program features include "two-finger pinch/zoom." Slide rule slide show images can also be rotated. Enlarge an image by double-tapping in the same place. Tapping three times in the same place will return the program to the home position. Tapping four times will bring up an intro-screen message which requires tapping anywhere to remove.


This program was first released in 2016 and is the product of a lifelong love of numbers (and 30+ years of programming experience!).

Special thanks to the Oughtred Society for their member's invaluable help in evaluating the earliest versions of this program.

What’s New

Version 4.06.08

This app has been updated by Apple to display the Apple Watch app icon.

Faster setup time after program is loaded (as much as 50% faster); streamlined internal processing (especially of Cylindrical Slide Rule); corrected "Display Estimated Hairline Values" for several of the alternate scales.

Ratings and Reviews

5.0 out of 5
10 Ratings

10 Ratings

Dragonite398 ,

Excellent — This program really surprised me.

The slide rules are rendered realistically — you get a sense of what it was like to use them. Plus I also love that the text and the slide rules are integrated. Great job!

F2959 ,

Absolutely Beautiful

Beautiful simulation of an actual slide rule with many variations of older slide rules.

Mazo Lerch ,

Calculate without using buttons!

This is awesome an App and it will help introduce the slide rule to those that were not required to use them prior to electric calculators being developed.
+ Using this App in landscape mode really makes it wonderful!

App Privacy

The developer, Ace Hoffman, has not provided details about its privacy practices and handling of data to Apple.

No Details Provided

The developer will be required to provide privacy details when they submit their next app update.

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