Calculators are one of the most primitive forms of computers. Most of them (except some scientific types) help you do very basic calculation and displaying the data or results (and now-a-days the mathematical operators) but only one at a time always.
Excel is the most advanced technology when it comes to number crunching and calculation. And the best thing is you get to see all your data and the results all in one place. But it is a pity that those who have access to Excel in their computers that are sitting right on their tables (and laps and palms) still tend use the primitive calculator. This happens most of time due to ignorance of the capability of Excel and the ease with which Excel can be used.
Enter the data in cells and selec the respective cells. That is all you need to do in Excel to see the results. The status bar at the bottom displays various results - Sum (sigma X), Count (Count for number of selected cells and Numerical count for number of cell that contain numerals (sigma n)), Average (Sigma X/Sigma n), Maximum (the largest number in the selection) and Minimum (the smallest number in the selection). And all this at a time. (The difference between the maximum and the minimum is called the Range).
When you want to make a change in the data and see the effect of it, you do it much easily in Excel. Just change the data in the cell or cells and the respective result also changes. And you want to revert, do a Ctrl + Z. And you want to retain the change - Ctrl + Y.
When you want to display the result in cells, you go a step further to enter the formula or use a Keyboard Shortcut or a mouse click (two in the case of the sigma).
So much luxury Excel offers and it is the user who has to exploit its power to save effort and time.
All the best!