How do you like the Woodstock calculators?

[jwr]

I consider the HP-25C my most useful calculator. To provide some context, I also own and use these models: HP-50G, HP-48GX, HP-12C, HP-11C, HP-15C, HP-16C.

Why does it work so well? First, it has the perfect form factor: it can be used while held one-handed (my main gripe with the Voyager series). Second, it has a great set of features, everything that's needed for quick engineering work without stuff that is really better done on a computer these days. Overall it strikes a good balance.

The battery pack and the catastrophic charger were a real problem, so I built my own wireless charging module for it (https://partsbox.com/blog/wireless-charg...-2021.html). It had two interesting side effects: one, the calc with the LiPo module is lighter than a HP-25 with NiCads or alkalines, so it's more likely I'll have it with me, and two, the pack works so well that I actually rarely have to worry about charging.

Now I use my HP-25C every day and it's my favorite calc. I think the HP-90 comes second (when I need unit conversions) and I prefer the HP-12C for financial stuff, mostly because of the %T and delta% keys.