I have always preferred some kind of physical calculator for doing calculations. I never need to do excruciatingly complex math, but I have a cherished TI-34 from the early 90's that I have dragged through college and 3 jobs. Full scientific calculator function with 0 batteries, it runs just on its tiny solar panel and the soul-sucking fluorescent office lighting, which is the one feature that keeps me clung to this particular model.