Slide Rule Museum

400 years since the discovery of the logarithm!

Keep ISRM Free!
ISRM is the world's largest free digital repository of all things concerning slide rules and other math artifacts. There are over 7000 Images or PDF's in the ISRM Galleries and Libraries. Mission: ISRM is dedicated to the Students, Educators, Scientists and Engineers of the Past and Those Still Present, and to promote the lost art of Numeracy by providing resources and slide rules for education and other historic institutions. We accept donations of slide rules for inclusion in the galleries. ISRM is a member of the American Association of Museums and the Association of Northern Front Range Museums. ISRM was founded in 2003. Our apologies, the site is not mobile-friendly.

48% of goal - 18 donors as of Dec 31
2016 Annual Fund Raiser - ISRM needs to raise a minimum of $2000 annually, necessary for its programs, exhibits,and ongoing web maintenance. In our 13th year of being on-line, we currently average almost 1 million hits/month with 60 GB of data being downloaded from 118 countries, all at no cost to you! There are no paid staff members, but we need help in keeping ISRM growing and on-line during these challenging times. In 2011 ISRM established a FRIENDS OF THE MUSEUM page to acknowledge its many supporters. You can become a TIER 1 FRIEND OF THE MUSEUM by your donation through Paypal or by check. You can also help by participating in ISRM's Slide Rule Rescue program where you can adopt slide rules. Thank you for your welcome support and kind consideration!
Mail checks or donated items to: Mike Konshak (ISRM Curator), 1944 Quail Circle, Louisville, CO 80027, USA.

Welcome! Click Here for Introduction, Museum Mission Statement, and Donation Policies.
Visit What's New! for the latest additions to the galleries and changes to the website.

Slide Rule Galleries
All slide rule specimens, scans, photos and ephemera are organized into one of 50 galleries; by major manufacturer, construction style, country/region, time period or application. Scroll down on the MENU on the left to go directly to a particular brand or to see other data.
Aristo - D&P
Eastern Europe
HSR Catalogue
K&E Standard
K&E Specialty
Nordic (DK/SE)
Orient (East Asia)
Pocket Watches
Rarities (Olde)
Slide Charts
United Kingdom
United States
USSR-Soviet Era
Who's Who

Slide Rule Library
Scans of slide rule manuals and text books are organized into one of 13 areas:
Library Main Desk
Elect. Calculators
General Purpose
Books and Text
United States
Kueffel &Esser

News for Friends of the Museum
See What's New for recent additions.

Slide Rule Rescue - Adopt a Slide Rule ISRM is a program to raise necessary funds to continue its all free services to the slide rule community. You can help in this effort by adopting one or more slide rules that are duplicates in the museum. To buy slide rules that may be on eBay (search seller ID i-s-r-m) or visit the ISRM Slide Rule Rescue page to adopt a slide rule. All adoption funds go toward maintaining the museum website and supporting the Slide Rule Loaner Program for Schools. In addition, if you would like T-shirts or mugs with the ISRM logo you can order them through Cafe Express. ISRM receives 20% of all sales. Note: Donated slide rules, associated with family members, will never be sold. They become part of a permanant archive for preservation. The specimens they replace, however, may be items in the fund raiser.

You can now buy t-shirts, mugs & gifts with the ISRM Logo from the museum's souvenir shop.
2012 marked the 40th anniversary of the HP-35 'Slide Rule' Calculator
(and the beginning of the end of the slide rule industry by 1977).

The release of the Hewlett-Packard HP-35 occured on Febuary 1, 1972. the HP-35, named for the number of keys on the calculator, was the single most instigator of the demise of the slide rule as we know it, even though the introductory price was $395.00 or $4000 in 2012 money. Within months, Texas Instruments released the TI-2500 4-function calculator and the SR-10 slide rule calculator.
Visit ISRM's Gallery of Slide Rule Calculators from 1972-1977

Gold: Werner H. Rudowski(center)
Silver: Jörn Lütjens (right)
Bronze: Klaus G. Krämer (left)
The Deutschsprachigen Rechenschieber-Sammler RST (German speaking Slide Rule Collectors) held its 23rd annual meeting in Altona (Hamburg) Germany on April 14, 2012 and hosted the 2012 'truly' International Slide Rule Championships, the first one to be held in Europe. 15 of the 40 slide rule collectors, 5 countries (Germany, Switzerland, The Netherlands, Luxembourg, and Finland) volunteered in participating in the International Slide Rule contest (Continental European) 2012, which was performed for the first time. The main profession of the contesters were (retired) engineers, 2 active pilots, and teachers. All the participants received an ARISTO Darmstadt 967 slide rule and had to solve 10 problems within 30 minutes.
The champion, Werner H. Rudowski won with with 10 (all) solutions solved followed by Jörn Lütjens with 9.5 solutions and Klaus G. Krämer with 9 solutions. Congratulations all!
Any collector group, school or engineering association are invited to host an ISRC contest.

ISRM is administering the International Slide Rule Championships. Any collector group, school or engineering association are invited to participate. Problem sets provided by ISRM as well as the Medals to be awarded to the local champions, FREE! The first innagural contest in was Rose Suarez's Mathematics and Research Class in Half Hollow Hills, NY. (on Left). Kristen Fouss's Pre-calculus class at Anderson HS in Cincinnati, Ohio had the most recent champions (on right).
Mike Konshak, ISRM Curator presented a symposium on slide rule history, manufacturing processes and use to the Northern Colorado No. 354 chapter of the Society of Manufacturing Engineers in Longmont, Colorado. Mike was presented with an award by Andy Keller and Don Larsen and many slide rules were donated to ISRM by Andy Keller from his personal collection. More pictures.
Interesting Features at ISRM
  • There is a Search Engine for this website which will assist you in your research of slide rules. This Search engine is provided by JRank
  • The Slide Rule Scales can be used to build your own slide rule. The latest uses a CD/DVD case to support a circular slide rule (by Ying Hum of Canada)
  • Technical Slide Charts and Disks. Over 700 pre-programmed calculators made of cardboard or plastic film for designed for specific repetitive tasks and offered as promotional items.
  • The Slide Rule Who's Who - Past and Present gallery shows slide rule manufacturers, inventors, dealers and active collectors and donors to ISRM.
  • The gallery of Historical Photos of People with Slide Rules. Over 400 Photographs and Ephemera showing slide rules in action is constantly being expanded.
  • The Patent Database. gallery is useful for research. Downloadable Patents as early as 1851 to the present day, involving logarithmic calculating devices. There are currently over 900 worldwide Patents available for downloading in PDF file format.European patents are sadly incomplete at this time.
  • The gallery of Herman van Herwijnen's Slide Rule Catalogue has clickable thumbnails to over 2200 slide rules and slide charts.
  • The ISRM's Free Slide Rule School Loaner Program now has many new sets for use in the USA, Germany, Netherlands and Japan. Teachers may now keep them out for a full semester! The program has been expanded to include Home Schoolers.
  • Free Web Hosting for ISRM Associates Put your collection here!

Students from the Collège André-Grasset in Montreal, Canada using slide rules donated by ISRM. Click on the banner for more information.

Students from the University of Waterloo in Ontario, Canada created an exhibit for the annual Knowledge Integration (KI-X 2011) exhibit using slide rules donated by ISRM. Click on the banner for more information.

Dr. Barbara Rooker of the Joplin, Missouri K12 School System, introduced students to slide rule math during 2009 using ISRM's free loaner program. Click banner for more pictures:

The original specimens and files found in this museum prior to 2005 were donated to the Computer History Museum in Mountain View, California in for preservation and display. Take time to visit CHM when you are in the area. ISRM continues to expand with replacements through the generous cooperation and donations of collectors and heritage donors from around the world.

Modern Logo's depicting Slide Rules

USAF Test Pilot School Patch, Edwards AFB, California

Joe Miner, Official Mascot of University of Missouri-Rolla, now the Missouri University of Science and Technology
Purdue Engineer's Yell (1960's)
e to the x, dy, dx
e to the x, dx
cosine secant tangent sine
three point one four one five nine
square root, cube root, Btu
slipstick, slide rule, Yay Purdue

Contributed by Bruce Chelf,
Purdue Alumnus (The ISRM curator
subsitutes CSU for Purdue)

* Hairy-Eared Engineer - definition:
1) An engineer who's old enough to have hair growing out of undesirable places.
2) Who's been practicing engineering so long that he or she has already made all possible mistakes at least once.
3) A desirable person to have on a project to ensure the mission succeeds.
4) Quote: "Every project needs at least one hairy-eared engineer" Marvin B. Davis -1980.
(Marvin was one then and 34 years later, my barber can attest that I've finally made the grade).

Slide Rule Wallpaper

This wallpaper is a collage of many slide rules. It is 1240 x 1020, 582kb and I have almost every slide rule manufacturer and country represented. Save this file (Right-Click Save Target) and select it using for the background on your computer monitor. 'Right-Click' on your screen and select 'Properties', then 'Browse' to the file to change your wallpaper. I hope you enjoy it.

Astrological Nerd Signs - A Y2K Compliant Zodiac

Keuffel and Esser, the Slide Rule
Keuffel and Esser, the Slide Rule
September 24th ~ October 22nd

People born under the sign of the Slide Rule have a particular talent for extending themselves to handle new problems and situations. They are able to look at problems, both small and large, and immediately keep the basic details in proportion. Elegant and dependable, Slide Rules are known for keeping their cool and never letting on that they're being pulled too far until they reach their limit and abruptly fall apart.

Not you? See where your birthday falls in Nerd Signs
Proud Member of

1550-1617 John Napier Invented the Logarithm in 1614

1574-1660 William Oughtred Inventor of the Slide Rule

1831-1936 Victor Amadee Mannheim standardized modern scales

c1890 DUPA (Aristo) Class Germany

c1900 Englewood (NY) High School Students

c1905 IIT Classroom

1909 IIT Elect. Engineers

1934 Iowa State SR Class

1941 IIT Engineering

1942 Purdue Aeronautics

1950 African-American Students.Prarie View, TX. Texas A&M

1952 Edwards AFB
Test Pilot School

1954 Hamburg, Germany

1957 Robert Herndon, Aircraft Engineer (Life Magazine)

1965 NCF Math Class

1970Colorado School of Mines

1976 Joe Pasquale (right) Weehawken HS, NJ now a Professor at UCSD

1980's "Startrek" TV Re-Runs

Present Collector

Mike Konshak, the curator and webmaster of the museum, now (2015) on the Board of Directors of the Oughtred Society. He was honoured with the OS Award for 2009 and made a Fellow in this prestigious organization in 2006. It is an honor to be selected to be amongst the other current and past Fellows and Award winners. If you are the least bit interested in the history and use of slide rules you will want to join the Oughtred Society.

Copyright © 2003-2015 International Slide Rule Museum