Product Review: HP-35S


After a number of years of disappointing the almost rabid fans of the HP-15C and the HP-41 calculators, it seems as though HP may either be listening to the fans or at least coming to their senses. Exhibit A is the new HP-35S which seems to have come out for the 35th anniversary of the original HP-35 (shown on right) which was their first pocket calculator and the world’s first scientific pocket calculator. Whatever the reason, I think HP has produced a fine product.

As good as the 15C? Nope, ‘fraid not.  The only hope of that would be a remanufacture of that classic. Considering the amount even a beat up one can fetch on e-bay, HP could probably make a fortune if they did resume production (sign this petition if you agree). By the way, there are two great iPhone/iPod touch applications that emulate the 41 and the 11c.

Not perfect, no, but the 35s is still a great calculator with many of the features we love about HP calculators.  First, of course is that it is RPN. Yes, there is an algebraic mode too, but I’ve never bothered to try that out. The RPN works as well as ever – I really don’t understand why anybody would want any other method.

The keyboard is almost as good as the old calculators but you can feel the difference with these new, Chinese pads. decent clicks and feedback, but just not as solid as the old ones. The calculator has all the functions you’d need, though there are some changes in placement that have created some complaints. Notable of these is the STO button which requires a shift button first. No big deal, to me, but the layout could be improved a little. Welcome new functions include conversions and a ready library of physical constants. Very handy.

The form and look of the calculator is somewhat retro but I think it is a handsome look and though it is a little big for a shirt pocket (it still fits); it fits the hand nicely. Sitting on the desk, however, creates a bit of glare in the display. Nothing too drastic, but it can be annoying under some soul-sucking office fluorescent lighting. The display is two-line which makes it a bit easier to remember what’s in the stack.

Actually, one of the common complaints about the case is that the sides aren’t quite straight. I guess people used to use the old cases as impromptu straight edges out in the field. I, for one, don’t mind the slight curve.

I can’t really comment on the programmability of the thing, but from other reviews it seems adequate, with both label and line number addressing (a problem with the 33s which only had the 26 labels to work with).

All in all, I think this is a really good attempt by HP to get back to the proper roots of their legendary calculator line. I just wonder how much longer RPN calculators will be around at all. For that reason I’m going to pick up another 35s as a spare, and keep looking for a cheap 15c.

See more reviews and pick one up (around $50 US) at (link).


11 thoughts on “Product Review: HP-35S”

  1. Good but flawed. I bought two and there are some frustrations but generally a vast improvement on the 33s. Nearly there!


  2. Agreed on the improvement on the 33s. I don’t know why they put the effort into that one – all the design changes and all – when all they have to do is resurrect the 15c.

    The one frustration I have found lately with the 35s is in the conversions. I really have more use for feet to meters rather than inches to cm. I can remember 2.54, not so much the other.


  3. Key suggestions for change HP35S:
    1 – direct access to STO.

    2 – alphanumeric variable (as HP41CV).
    Possibility to put variables with alphanumeric names,
    ie pressure instead of P!

    3 – Alpha Alpha to alphanumeric changes (as in HP48SX, allowing you to enter words directly (without rcl rcl rcl …). Or a button as the alpha HP41CV!

    4 – Button polar to rectangular and vice versa.

    5 – customizable keyboard, as in HP41CV and HP48SX. Essential for those who program the calculator and use the same engineering.
    Masks plastic keyboard as in HP41CV!

    6 – online catalog of buttons to access the program catalog, catalog of variables, constant catalog, catalog of conversions.
    —– catalog ———
    prgm var const

    7 – conversions -> F -> C -> lb -> kg -> mile, -> km,> in -> cm, can be moved to the menu that shows a result of the conversion directly. Working as menu estimate or estimate of x and y.

    8 – possibility of adding and subtracting direct hms!

    9 – functioning as E3 1000!

    10- plastic mask for keyboard, like 41cv!

    Other sugestions:
    1 – Return off HP15C (with more memory)
    2 – Return off HP41CX (with more memory)


  4. Man, this thing ( hp35s ) is a shocker for one main reson – the decimal point gets lost between the numbers, especially the number 2. After using the hP42s for 30 years this thing is going in the bin where it belongs.


  5. I have found that the 35s does not always register keystrokes! When adding a column of numbers with 4 to 6 digits is when it usually happens & also when inputting a number with repeating digits, eg 25558 comes up as 2558. Not good as the total is obviuosly wrong. After years of 32S use it’s difficult now to learn to watch the display for confirmation of the correct entries.
    Incidently have experimented with someone watching & confirmed the keystroke being made but not comming up on the display.
    This is a replacement 35s by the supplier for the first one I bought when I reported the problem under guaratee.


    1. Yes, I’ve seen a few instances of that too. Not enough to stop using it, but certainly need to keep an eye on the display. I had a similar issue with the HP-50, but there is a setting for the delay so you can usually fix it. I don’t know if there is a way to do this on the 35S.

      So far the 15C LE keyboard has been very dependable.

      Thanks for the comment.



  6. Just sent one of these back to Amazon the ‘7’ key did not work at all. I also assumed for the money it would have a proper piece of glass over the display – no such luck. Not quite as cheap feeling as an £8 Casio but to be honest, not far off


  7. I have had an HP 35S for about 5 years now. The keyboard is a disgrace and always has been. The zero and the eight usually fail to register, even with slow, persistent touch. It takes three or more pushes to get them to function. Compared to my old 15C (display finally died after 20 years of brutal laboratory use and many falls) this has been a huge disappointment. Made in China.


  8. Display scramble issues?

    My 35s recently displayed some scrambled display symptoms that corresponded with a locked-out keypad. Had to pull batteries and then reset to recover. Left on for a bit, and scrambled display returned – but not consistently.

    Anyone else have a similar issue?


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