[flysand7]

The biggest thing I'd want from a calculator -- having to calculate numeric expressions involving units, and getting the result in a specific unit. This is something I've used the google search prompt for because it can do these things to some degree, but google isn't a calculator and it will refuse to give you an answer right away if it doesn't think you entered a valid numeric expression.

Most of the time I'm looking for an answer in questions like:

    4 weeks + 59*3 hours in days
    1/2 * 36g * (900 m/s)^2 in joules

Other times when I'm working with memory and want to get a specific finite representation in hexadecimal:

    1 megabyte as hex

This might be off-topic because you're building a suite of calculators that I'd have to switch between to perform these tasks, rather than a single calculator that can do all / most of these things, but this kinda raises a point - if you want to switch between the calculators, maybe the UI should allow going from one to the other without performing the navigation, I'm thinking something like a sidebar that you can click on to switch to a different calculator.

Ideally when you switch and switch back the state should be saved because you might need to copy multiple values between calculators. EDIT: I forgot browsers have tabs, but still.

But really for me personally, nothing would beat a single thing that can do units and bases

[Ao7bei3s]

Try https://numbat.dev/ (https://github.com/sharkdp/numbat). It's my go-to for any engineering calculations. It can also run locally.

  >>> 4 weeks + 59*3 hours -> days
  4 week + 59 × 3 hour  day
      = 35.375 day    [Time]

  >>> 5V / 50ohm -> mA
    5 volt / 50 ohm  milliampere
        = 100 mA    [Current]

Full syntax: https://numbat.dev/doc/example-numbat_syntax.html

[paradox460]

I like numbat, but wish it supported rpn

[tjelen]

This one is basically my daily driver for similar tasks: https://app.heynote.com/ (full app at https://heynote.com/). And it seems to work almost out-of-box for your first two examples, once you switch the buffer from "Plain-text" into "Math" mode.

It also supports switching between different buffers and some kind of local storage.

[onedognight]

What you want is WolframAlpha.com. Your examples[0][1] work out of the box.

[0] https://www.wolframalpha.com/input?i=4+weeks+%2B+59*3+hours+...

[1] https://www.wolframalpha.com/input?i=1%2F2+*+36g+*+%28900+m%...

[exmadscientist]

The old TI-89 handheld calculators are amazingly good at this stuff. (It does struggle with "bytes", though it handles hex quite nicely within its syntax.) I still have one on my desk, and this is the main reason why. I barely bother with it for anything that doesn't involve units, and it's still worth the literal desk space. There is a good Android emulator, though in recent years it seems to have grown the habit of sometimes registering taps as a large number of button presses. I'm not entirely sure why; this behavior is very annoying. It might be phone-dependent, or a problem caused by a too-new Android version.

Frink is also very good at units, but I struggle to use it for anything more complex than a simple conversion. I'm sure it can do the task, but I've never been able to learn to drive it well, and usually get pretty frustrated when I try. The documentation and my brain don't really get along, or maybe it's that I am often in a hurry when I am trying to do something with it.

[calculatehow]

No you raise a great point. It's something I'm trying to solve. In the past, I've also had annoying issues where calculators didn't allow for multiple input types or wanted the input in a weird format. Good to know that more people have this problem. Thanks for sharing!

[paradox460]

This is one of my favorite features of my old HP-50. You can attach units to numbers, and even define conversions between units.

[ttshaw1]

Try qalculate. It's great with units and I think will work for base conversions, though I haven't tried that