Getting an average difference of two dollar amounts, like currencies or other financial data, can be useful for tracking change over time. When calculating an average percentage between two different dollar amounts, you first determine the difference between the two figures. Next, you take an aggregate of those different percentages over time and find the average difference, which is a division problem. You don't need access to calculus or other higher math to solve this type of problem. A paper and pen along with a calculator will do.
Subtract dollar amount B from dollar amount A to get the difference. For instance if dollar amount A is $344 and dollar amount B is $322, the difference is $22.
Repeat this step for dollar amounts A and B over time, or for each data pair. You may get a negative number if dollar amount B is larger than A. That is fine.
Add the total differences you have calculated. For example, if the differences are $22, $41, $21, -$3 and -$12 in a week, the total difference is $69.
Divide this resulting figure by the number of data pairs. Here, $69 divided by 5 yields $13.80, the average difference between dollar amounts.
Sum the total of dollar amount A or B, depending on which dollar amount you wish to express the average percentage in relation to. You will get a different percentage depending on whether you calculate for the percentage of dollar amount A or B, unless the sums of those amounts happen to be equal. If your dollar amounts A were $230, $254, $210, $198 and $218, the total would be $1,110.
Divide the sum of the dollar amounts by the number of data units. For this example, $1,110 divided by 5 is $222.
Divide the average difference by the result to express the average difference as a percentage of your selected dollar amount. Here, $13.80 divided by $222 is 6.2 percent.
Bill Brown has been a freelance writer for more than 14 years. Focusing on trade journals covering construction and home topics, his work appears in online and print publications. Brown holds a Master of Arts in liberal arts from St. John's University and is currently based in Houston.