HP 65

HP 65

This fairly hard to find Hewlett Packard made HP 65 calculator was produced from 1974 up until 1977 and retailed for $795.00.  It was HP’s first programmable pocket calculator and had a built in magnetic card reader – writer.  It featured a single line red LED display and used RPN logic. It was also HP’s third scientific calculator. It is known for being used in 1975 by the astronauts of Apollo to make calculations that helped them dock with the Soviet space station Soyuz. The HP-65’s were used as backups in case the main computer system on the Apollo went down.

The HP65 was the first appearance of the “Tall” keys where each key had the capability of implementing 4 functions.  As you can see, each key has a function on its face, one listed above the key as well as one on the forward face of the key. By pressing the yellow second function key the user could access the inverse of the function listed above the key.

HP 65

HP made a subtle design change with the HP 65 as well. As you can see in the picture below the older HP-35 on the left has a silver trim line going under the display and above the on/off switch. This silver trim would wear quickly, as it has on this calculator, when the calculator was turned on and off over time. So, with the HP 65 the trim was repositioned around the top of the display and away from the on/off switch. This kept the calculator looking newer longer.


The HP-65 could read from and write to magnetic cards.  So, the user could input their own programs, of up to 100 lines, into the calculator and save them to the magnetic card. They could also use pre-programmed magnetic cards that came in what HP called “Pacs”.  The HP 65 came with a “Standard Pac” of 40 magnetic cards that contained 19 programs. There were also additional “Pacs” available including:

Aviation Pac 1                  Chemical Engineering Pac 1
EE Pac 1                          EE Pac 2
Finance Pac 1                  Machine Design Pac 1
Math Pac 1                      Math Pac 2
Medical Pac 1                   Navigation Pac 1
Stat Pac 1                       Stat Pac 2
Stress Analysis Pac 1       Surveying Pac 1

HP 65 Pac

The HP 65 came with a hard plastic case for the calculator and accessories as well as a soft leather case for the HP 65 itself.  Accessories included the HP-65 reference guide, HP-65 Owners Handbook, Power supply, and Standard Pac magnetic cards.

HP 65 Box

The fully functional HP-65 is a difficult calculator to find and prices reflect that. Many times the card reader does not work as the reading mechanism gets gummed up over the years. Still, a fully functional HP-65 will sell for around $400.00 alone. Throw in the original case and accessories and the price can reach $700.00.

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