RPN-35 SD — The first photo-realistic HP-35 simulator for the iPhone

Version 1.4

RPN-35 SD is a photo-realistic simulation of Hewlett-Packard's break-through scientific hand-held calculator.

On January 4, 1972, Hewlett-Packard announced the HP-35, world's first scientific calculator small enough to fit in a pocket - more precisely, Bill Hewlett's shirt-pocket. The HP-35 was an immediate hit with students, engineers, and scientists. Despite its steep price of $395 (more than $2,200 today), it sold ten times better than anticipated in the first year. It was discontinued in 1975.



Tap the wrench symbol to access the settings screen:

Vintage Mode

In this mode, RPN-35 SD simulates a real HP-35 very closely:

    In Vintage Mode, the settings button (wrench) is shown in blue.

Enhanced Memory Mode

In this mode, available only if Vintage Mode is off, RPN-35 SD provides advanced register handling.

iPhone 6 Screenshots:

HP-35 Version 3

HP-35 Version 4

HP35 Back Label



Version History

1.4 – Oct 2, 2016
  • New:
  • • Improved results for SIN, COS, TAN with very large arguments
  • • Decimal addition/subtraction for higher precision
  • • Calculator sounds mix with background audio and have their own volume control

1.3 – Sep 2, 2015
  • New:
  • • If audio is playing on start-up, RPN-35 SD will not produce any sounds

1.2 – May 12, 2015
  • New:
  • • Added info about how to access settings screen
  • • Fixed non-volatile memory not working

1.1 – April 8, 2015
  • New:
  • • HP-35 version 1 (with red dot)
  • • Settings and Info buttons may be set to invisible
  • • Low-battery situation shows one decimal point unlit, as depicted in the HP-35 User's Manual

1.0 – January 18, 2015
  • First public version.


RPN-35 SD is available here:



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