Instructions: All operations and functions placing characters into the display window must use the screen displayed keys. The number keys 0 through 9 are for data entry, as is the decimal button. The other keys are operational keys. + is to add, - is to subtract, * is to multiply and / is to divide, while % yields a percentage (300*15%=45) and +/- is to negate the answer (after the % example, +/- yields -45). (Negation is the process of multiplying any number in the answer display panel by -1.) The = key gives a final answer. C clears all operations and the answer area, while CE clears only the last entry. The operational key acts on what is displayed with the number entered after it. For instance, to multiply 5 by 2: click 5, click *, click 2, click = for the answer of 10. Chain calculations are possible in logical order. After an answer has been displayed in the window, the next operation key clicked and following input value act upon the number in the display window. For instance, to multiply 5 by 2 by 5: click 5, click *, click 2, click = for the answer of 10, then click *, then click 5, then click =, for the answer of 50. Accuracy is good to the capability of your browser, generally 18 characters in the display window. NaN is an indication of an error in input or calculation; do the process again paying close attention to your input. You may cut and paste or copy and paste an answer into ANY other program. At this time, there are no plans to add memory stacks or to present other higher math operations to this calculator. See our Scientific Calculator for more options!