PCalc -- because it runs on every Apple platform since the Mac Classic: https://pcalc.com/mac/thirty.html https://pcalc.com/mac/thirty.html My other favorite

PCalc -- because it runs on every Apple platform since the Mac Classic: https://pcalc.com/mac/thirty.html https://pcalc.com/mac/thirty.html My other favorite calculator is free42, or its larger display version plus42 https://thomasokken.com/plus42/ https://thomasokken.com/plus42/ For a CAS tool on a pocket mobile device, I haven't found anything better than MathStudio (formerly SpaceTime): https://mathstud.io https://mathstud.io You can run that in your web browser, but they maintain a mobile app version. It's like a self-hosted Wolfram Alpha.