Product ReviewsHP 35s Scientific Calculator

Yea, RPN!

For years I used ALG calculators, and still do for simple tasks. The cheap, but functional Casios and Sharps work fine and have all the power to perform what I need. After getting an HP calculator and becoming familiar with RPN, however, the others seem awkward to use, especially for anything even slightly complex. I'm always having to either put partial results in some memory location or filling the screen with parentheses. I have a couple HP48 series calculators and they are wonderful tools but they're big. I've looked for a small and inexpensive RPN calculator and the HP35S, while not nearly as inexpensive as a lot of low end scientific calculators, is at least small and light. It has great functionality, a fine, high contrast screen, crisp keyboard and looks great. I've never had any other HP RPN calculators except a 28c, which isn't any smaller than the 48. I see a few other older HP models, but they command pretty high prices sometimes. The HP35S is great so far so I am hoping it has the robustness of its predecessors. That remains to be seen.Read full review...

Verified purchase:  Yes | Condition: pre-owned | Sold by: simeon707

Has Some Flaws

At first glance it seems like it would be a great calculator for those who don't want to use RPN but want a Hewlett Packard. I found the display very hard to read as it has a glossy cover on the LCS so there are lots of reflections. Also the digits themselves are made from oddly shaped pixels and appear fuzzy. The buttons are louder than the classic HP calculators which was always nice feature of older HPs. These make a louder click which can be distracting and feels cheaper than the HPs of earlier times. The HP 20S is less expensive if you find it has the features you need. It also uses algebraic input, not RPN.Read full review...

Verified purchase:  Yes | Condition: new | Sold by: seattlecellmarket

Very good modern calculator with most of the appeal of the old HP-15C

For many years I greatly admired the classic HP-15C scientific calculator from the 80s and had wanted to buy one for some time.

But they were always too expensive when they came up for sale second hand, plus compared to modern calculators the originals are very slow and the display is quite limited.

Then when HP released the new Limited Edition of the 15C last year with a promised 100 times speed increase over the original and a recommended price tag of $100 it looked as though I would finally be able to afford one and it would as fast as a normal calculator.

Unfortunately the whole stock was bought by a few retailers who immediately increased the price to two to three times the HP RRP making them still too expensive.

This forced me to reassess what I actually liked about the 15C and wanted in a scientific calculator of this type.

The RPN entry system, classic HP angled key style, ability to write and store programs and work in different bases were all important plus these days the ability solve equations and have a more informative display would be a vast improvement over the 15C.

Hence I looked at other HP scientific calculators and found the 35S, which has all the above features and many more and the only drawbacks compared to the 15C are that it doesn't look quite as classy and is in a more normal portrait format compared to the 15Cs landscape.

It also has lots of other advantages over the 15C, it can be used in standard algebraic or RPN modes, it has many more functions available, far more memory, various conversion factors and constants built in, a two line modern LCD display and is a much more reasonable price.

So I bought a 35S and I am extremely happy with it.

It is a complicated calculator and takes some time to get to know, probably even more so than the 15C since it has so many more modes and functions.

In fact I would recommend that anyone who buys one should decide fairly early on whether they prefer to work in normal algebraic or RPN mode and stick with the one mode.

Although it is easy to switch modes on the 35S if you try to use it in both modes for certain jobs it does get very confusing since the key entry for most of the functions is completely different in the two modes.

A fair amount of time should be allowed to learn how to use this calculator, with frequent reference to the user manual, at least at first.

In fact reading the user manual is pretty much essential with the 35S when it first arrives as there are so many functions and methods which are not immediately apparent from the keyboard and work in a different way to scientific calculators from other manufacturers.

In conclusion I would recommend the HP-35S to anyone looking for a non-graphing scientific calculator and especially to anyone who wants a modern day replacement for the old 15C.

Don Stewart.Read full review...

HP35s - an EXCELLENT buy!

I love the RPN notation on HP calculators. I have owned many since my college days and first learned the notation on my HP-35 back then. I've tried TI calculators with the ( ) keys but RPN is still more logical and easy to use.

I was designing a recent tool and needed more than a 4-digit machine (my 35 gave up awhile back). I researched the latest from HP and decided on the 35s. It has enough scientific capability and the RPN feature I like. Now that I'm an owner, I really like how I can store several programs at once and even work directly with fractions like 2 3/8 + 5 13/32 = ??? The 35s does it automatically!! Multiple conversions, a good feel, keys big enough for adult fingers - the 35s has it all!

For the few dollars it costs, this is the best buy in calculators!Read full review...

Calculator is exactly what a needed and was brand new!

I have used this type of calculator for decades and you cannot buy it in stores anymore. My current calculator just died and I am so thankful that I was able to locate a brand new one on eBay. Thank you!Read full review...

Verified purchase:  Yes | Condition: new | Sold by: tedselectronics1

Classic design with modern functionality

The HP 35s calculator uses two CR2032 batteries. The battery hatch is easy to open and clicks shut and remains locked in place. The display is clear and well defined. The HP 35s is a reliable hand-held scientific calculator. With its Reverse Polish Notation, this no-frills scientific calculator is very useful. Navigating all of the functions is very simple and straight forward. RPN is the default setting and is perfect for instant, super accurate answers.Read full review...

Verified purchase:  Yes | Condition: pre-owned | Sold by: malan_mac

A truly professional tool - great for the EE

Update (11/21/2017):

This is easily the most useful calculator I have ever owned. In a world where "powerful" computers are ubiquitous in the work place the HP 35S provides the PERFECT balance between a "pure calculator" and a computer. As one author wrote, this calculator can be as dumb or as smart as you need it to be.

In terms of power versus ease of use this calculator probably represents the pinnacle. It is not as powerful as the MOST powerful units, but it is still immensely powerful and soooo easy to use despite its great power. The following are key and core points that set this calculator among other legendary units manufactured by HP:

(1) The whopping 32K of user memory is more than enough for my Engineering task
(2) The complex number support is top notch. This feature is one key point among some others that makes this unit ideal for the EE!!
(3) No "extensive" searching among menus to find functions
(4) The programmability is superb and represents a remarkable improvement beyond other models
(5) Way to go with those built in physical constants
(6) The equation entry is excellent. I love the HP 42S, which is a GREAT machine, but I consider this feature a significant advantage over the HP 42S. It is often more desirable to simply key in equations than write programs to execute the same tasks
(7) This calculator has been around for more than a decade - this says a lot in my opinion.

One issue that has been reported by numerous users is the sometimes missed keystrokes. I have seen this on some units, but the keyboards are probably above average for the most part although I would not put them in the same class as the keyboards of the HP 41C or pioneer series for example.

All said an done, this unit has to go down as one of greatest calculators of all time. It is a REAL professional tool for the serious Engineer, and I am sure that this piece of innovation has helped spawn other innovations. The HP 35S is the perfect Engineering sidekick!!!!

This one is my favorite so far. I have bought several. The calculator is very easy to use, has lots of memory, easy to program, and provides marked improvement in the area of complex number operations compared to the hp 32sii. As a EE I really appreciate this. The dedicated "i" key is a dream come true for an Electrical Engineering type like myself.

My only complaint has to do with keyboard quality in terms of missed keystrokes on some units. Despite this, however, I am giving this one 5 starts because of the calculator's utility and engineering functionality. Thanks.Read full review...

Verified purchase: No

A more modern spin on a classic!

I love having a modern version of the groundbreaking HP 35 that I lusted over when I was in a high school trig class.

While I like RPN calculators, I wish they'd made the stack size larger. I've used a HP 28S for decades and have gotten spoiled by having a more or less unlimited stack, making entry of complicated formulas easier.Read full review...

Verified purchase:  Yes | Condition: pre-owned | Sold by: jerome6294

A supurb general purose Scientific Calculator

The HP 35S is a precision-made scientific calculator with great tactile feel and is ideal for general engineering and science calculations. It supports both RPN and Arithmetic operating system, and has lots of memory, programming features and about all the science and math functions you could ask for.Read full review...

Verified purchase:  Yes | Condition: new | Sold by: thefactorydepot

FE exam calculator

- I bought this to use on the Fundamentals of Engineering exam. It was one of two HP calculators approved by NCEES (neither of which I'd used) and judging just on looks, I picked the 35s over the 33 because it more resembled my old HP48. So far, I'm happy with it.

- Good reference: HP's manual is easy to understand and well-organized. It took me about an hour to get the hang of storing formulas in memory, then calling them up and entering arguments and solving.

- One con: the buttons have a "clicky" feel to them, but it's misleading, because they have to be depressed fully to have an effect (i.e., wanting "209", you pressed 2-0-9-, but "29" is what gets entered). I like this calculator but this is a big downside.Read full review...