Percent means out of 100, so 100 percent is a way to express the full amount of something. Viewing data in the form of percents helps you quickly evaluate what portion of a whole you are dealing with. Many areas of personal finance express data in percents, including interest rates, taxes and portions of your budget. Use simple calculations to convert raw data into percentages, and to use percentages to calculate pieces of raw data.
Data to Percentage
Identify the amount of the small part that you are working with. For example, if you are trying to calculate the percentage of your gross income you paid in income tax this year, the small part is the amount of income tax you paid.
Identify the amount of the large part, or the whole, of which the smaller part is a portion. In this example, the large part would be your total gross income.
Divide the small part by the large part to calculate the ratio of small to large. For example, if you paid $3,024 of income tax and your gross income was $51,259, then divide $3,024 by $51,259 to get 0.059.
Multiply the result by 100 to make it a percentage. In this case, 0.059 times 100 is 5.9 percent.
Percentage to Data
Identify the percentage that you are working with in a given situation. For example, your mortgage lender might tell you that your monthly payments can be a maximum of 26 percent of your gross monthly income.
Convert the percentage into a decimal by dividing it by 100. In this case, 26 percent becomes 0.26.
Identify which other piece of data you have. In this case, you probably know your monthly income, which is the whole from which you are trying to calculate 26 percent.
Multiply the whole by the decimal to find the part, or divide the part by the decimal to find the whole. In this case, if your monthly income is $4,700, multiply this by 0.26 to determine that your mortgage payment can be up to $1,222.