There are many kinds of calculators, but most calculators have the same standard keys that allow users to complete a variety of calculations. The number keys and addition, subtraction, multiplication, division and equal signs are all very straightforward, but the functions of the other keys are not so well-known.

Two very helpful keys on a calculator are "AC" and "CE." The first key clears the entire memory, and the second key only clears the last numbers that were imputed. The "%" key is used to calculate percentages. Users must press the "shift" key before the "%" key to get an accurate answer. The "pi" button displays the value of pi. To get an exponent while entering an equation, users should press the "EXP" button immediately before entering the value of the exponent. The last standard key is the decimal (.), which allows a user to input an equation that includes a decimal.

Most standard calculators also have memory buttons. The "Min" key allows users to save a displayed equation in the calculator's memory. Most calculators have enough memory to store 10 equations or answers. To input an equation manually, users press "M+" to add an equation or "M-" to delete an equation stored in the memory bank. To access an equation stored in the memory bank of a calculator, users can press the "MR," or memory recall, button.

Occasionally, it is possible to receive an error code on a calculator when the incorrect buttons are pushed. This happens most often when a user fails to hit the shift button when pressing keys that require this command. To clear the error message, users should press the "AC" button.