I have a very nondescript calculator called Numi that I discovered ages ago. I see it’s name now popping up everywhere. I use Numi to make calculations all the time as it sits in my menubar and is just so easy to access.
Numi is also easy to use. You write your calculations out, if you want, with natural language and the calculations take place. Numi has numerous little tricks all of which to make calculating something faster and easier. I find this to be one handy utility.