This is a good project with a nice clean UI and of course the nice lack of ads that calculator sites love to paint everywhere.
That being said, I do a lot of maths at my day job (and side job) and have found that now that I can ask my phone (gemini) math problems directly in an unsimplified form, its totally made online calculators irrelevant.
"Hey google, calculate the power loss of a 20 ohm resistor if it is R1 of an RC circuit with a 1u cap, an input frequency of 25kHz, and a rms voltage of 1.2V. Then make me an applet that shows the power loss with a slider for the input voltage from 1V to 12V, and a frequency slider for 25kHz to 250kHz."
I really cannot emphasize how helpful this is, and basically removed the need to seek out online calculators for common electronics calculations (which can now be folded into single custom calculations), which replaced the need to manually write out and solve the equations.
Thanks! You bring up a good point of new alternatives to calculators. Certain people don't need these calculator websites because assistants and even google can figure it out in the search engine results. I think calculators can play a role in helping the user understand what goes behind in a calculation.
Be careful doing that -- it's a great help (and I use LLMs for EE stuff too) but one thing LLMs still suck at is unit conversion. If you ever need to mix angular frequency (omega) and hertz, for instance, you'll need to tread VERY carefully. Same with anything involving gas laws, nuclear radiation, or vacuum tech, where there seem to be 20 different ways to express every quantity.
As for calculators, nothing I've found beats Jupyter QtConsole. It launches at startup and I have a hotkey mapped to bring up the window.