Kingson Pocket Calculator

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The Kingson Pocket Calculator is operated by a pointed stylus, shown clipped to the right hand side. Pulling the bar at the top resets all digits to zero. The first number is entered by placing the stylus into the tooth indicated by the digit scale and pulling downwards; the digit will then show in the central window. To add another number, the same process is used, except that if the appropriate tooth for the new digit is red, then the stylus must be moved upwards, around the loop at the top, and down the other side to carry one into the next highest digit. If the next highest digit is already a 9, then a carry into it will show in the window as an arrow pointing upwards. When this occurs, the stylus must be placed in the 0 tooth for that digit and moved right up and around to carry one into the next digit. If you try to add 1 to say 199999 then you will have to do this four times before the result shows as 200000 (successively: 199999 - 1999'0 - 199'00 - 19'000 - 1'0000 - 200000).

Subtraction is much the same except that the lower set of teeth are used, movement is upwards for white teeth and downwards for red, carry involves going right to the bottom and back up again, and overflow shows as a downwards arrow corrected by a full downwards movement.

In the UK, these instruments were mostly used for money, and they were specially-designed for the eccentric English currency of the time, with three decimal columns for pounds, two columns for shillings with the left-hand only having 0 and 1 (20 shillings to a pound) and a single column for pence with slightly smaller teeth to allow numbers up to 11 (12 pence to a shilling). I had to try quite hard to get a pure decimal version. The UK changed to decimal money only in February 1971. Fortunately this was before the electronic calculator became widely available, otherwise I expect we would have had to buy specials for the UK market to do money calculations. Before 1971 I used to use a slide rule when abroad for quick currency conversion, but of course this required mental conversion to decimal and back.

Our calculator complete with the original box, instructions and soft case were kindly donated by Peter Salt

Thank you to for the above specification

An interesting insight in to the use of the Kingson has kindly been provided by Richard Ling - see below and the attached example. 

Is an article from the Book "The RAF Britannia and Its people 1959 to1975". I was a Loadmaster on that aircraft for 7 years where weight and balance or load control was the Loadmaster's responsibility where one of my primary functions was to provide the trim sheet 'copy attached' which indicates to the aircraft captain or pilot the number of "souls” on-board plus baggage/cargo figures and their positions. So as a result, this document also shows that the center of gravity of the aircraft is within balance limits plus the all up aircraft weights are also within their limits.


The centre of gravity position is represented in the form of a diagram for simplicity, whilst the trim sheet will also show "the ideal trim line” advising the user how close they are to ideal trim. What I used to speed my calculations, to ensure a quick turn-round on military exercises, was a ‘Kingson’ Pocket calculator, the computer of its day. Operated by a pointed stylus, clipped to the right side.

Today Electronic Flight Bags (EFB) generate Load and Trim data for some aircraft flights, especially but not only cargo flights. The flight crew have an EFB which they use to calculate aircraft performance data, which takes account of the completed load and trim sheet. They also use the EFB to make the load and trim calculations themselves, so that once it has been checked, all that is required is that a copy be left at the point of departure. Normally press button with an electronic readout it sits in a small panel adjacent to one of the pilots seat.

A 'Kingson' is now exhibited at the Centre for Computing History so you now have one history of its use to back it up.

I hope this information is useful


Richard Ling

Manufacturer: Kingson
Date: 1965

This exhibit has a reference ID of CH10923. Please quote this reference ID in any communication with the Centre for Computing History.


Kingson Pocket Calculator

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