One calculator is just not enough when doing calculations, and a spreadsheet is too complicated. Here is calculator grid to the rescue, it gives you multiple calculators on the screen at the same time. It's a universal app, so it works on both iPhone and the iPad. Also, provided is handy dandy quick copy/paste buttons. On the iPhone you get 4 calculators on the screen at one time, and on the iPad you can configure with row and column sliders to get more calculators. Great for doing quick calculations that require separate numbers like tips, sale discounts, etc. Quicker and more simple than using spreadsheet program.