UK's largest public display of slide rules opens at TNMOC

Post this page to popular social media

Between the abacus and the computer came the slide rule

The diversity of slide rules, the analogue predecessors of digital computers, is celebrated through the newest exhibit at The National Museum of Computing (TNMOC) at Bletchley Park.

Curated by the UK Slide Rule Circle (UKSRC), the display of more than 40 British slide rules spans three centuries and shows the variety of shapes, sizes, materials, and purposes of this sophisticated calculating device. The earliest exhibit is the wooden Gunter’s Rule, first used in the mid 17th century by navigators and astronomers, and the most recent is a 1960s/70s Photographic Interpreters’ slide rule made by Blundell Harling.

Invented in the 1620s, soon after the publication of the concept of the logarithm, slide rules were in use right up to the 1980s. Their decline began in the 1960s with the advent of electronic computers and calculators.

“For 350 years the slide rule was the world’s pre-eminent calculating device and its design needed remarkably little modification to maintain its dominance,” said Colin Barnes of UKSRC. “In contrast to modern calculators, slide rules were never throw-away items. One or perhaps two would be used throughout a career. They are marvellous pieces of engineering and craftsmanship and the display at The National Museum of Computing pays tribute to slide rule designers and users across the centuries.”

“We often wonder how we manage without computers – and this slide rule display indicates just how we did,” said Kevin Murrell, a TNMOC Trustee and Director. “We’re delighted to work with the UK Slide Rule Circle to bring this hidden piece of history to the general public. It is of tremendous educational value and we know that will be of great interest to our ever-increasing number of visitors.”

Always popular with the tax man, one exhibit dating from 1775 is a wooden four-sided volume-calculating slide rule used to determine the amount of spirits in a barrel. Another, a circular slide rule with 18 gauge points enabled the rapid computation of interest payments.

Other professions and trades were also enthusiastic users of slide rules: Ewart’s Cattle Gauge from the 1840s has an integrated tape measure to calculate the live weight of cattle and percentage of meat on the bone; and the Timber Rule from the 1920s was one of the first industrial applications of the slide rule and was used to calculate timber volumes (making allowances for bark thickness).

The UKSRC and TNMOC have jointly published a ten-page booklet, A Brief History and Types of Slide Rule. It is available for £2.50 including p&p from

Notes To Editors

About The National Museum of Computing at Bletchley Park

The National Museum of Computing at Bletchley Park, an independent charity, houses the largest collection of functional historic computers in Europe, including a rebuilt Colossus, the world’s first electronic programmable computer.

The Museum complements the Bletchley Park Trust’s story of codebreaking up to the Colossus and allows visitors to follow the development of computing from the ultra-secret pioneering efforts of the 1940s through the mainframes of the 1960s and 1970s, and the rise of personal computing in the 1980s. New working exhibits are regularly unveiled and the public can already view a rebuilt and fully operational Colossus, a working ICL 2900, one of the workhorse mainframes computers of the 1980s, and many of the earliest desktops of the 1980s and 1990s.

The Museum is currently open on Thursdays and Saturdays from 1pm. For more information, see

About The UK Slide Rule Circle

The UKSRC was formed in the mid 1990s as an informal group of slide rule enthusiasts to provide a discussion forum and enable contact between members. Its newsletter, Skid Stick, is published three times each year.

For more details, see

Support us

The Museum has not received government or Lottery funding, so your help is needed.

Become a member »
Make a donation »
Become a volunteer »
Sponsor us »

Latest Tweets Follow