Type the amount number into your calculator. The amount number is the smaller number that you are using to obtain a percentage. For example, if you're trying to find out what the percentage of $50.25 of a $400 restaurant bill is, 50.25 would be the amount number.
Press the divide key. The divide key usually appears as a horizontal line going across with a dot above and beneath the line.
Type in the base number. The base number is the larger number from which you are trying to extract a percentage. For instance, if you are trying to find out what the percentage of $50.25 of a $400 restaurant bill is, the base number would be 400.
Press the equals key. The equals key appears as two parallel horizontal lines ("="). For some calculators, the equals key is instead marked as "Enter." If so, press "Enter." A new number should appear.
Press the multiplication key. The multiplication key is marked with two diagonal lines crisscrossing with each other ("X").
Type "100" onto the calculator.
Press the equals key again. The number that appears is the percentage you are looking for. For instance, the percentage of $50.25 of a $400 restaurant bill would come out to 12.5625%.
For the sake of narrowing down the numbers after the decimal, only use the first two numbers after the decimal. Therefore, the percentage in the example is 12.56%.