Working with formulas and functions
A formula calculates a single value based on constants (such as 1.07 or “hello”), operators (such as “+” or “>”), and field references (such as Subtotal or InvoiceTotal) you enter. For example, if sales tax in your area is 7% and you have a field named Subtotal, you could create a field named InvoiceTotal that gets the value of the formula Subtotal * 1.07.
If a formula is especially common or popular, FileMaker Pro gives it a name and defines exactly how you should use it. A named and predefined formula is called a function. For example, if you want to find the average of some test scores, you could write your own formula to add them all and divide by the total number of scores. A simpler approach would be to use the function named Average and follow the rules defined for its use.
Related topics 
Functions reference (category list)
Functions reference (alphabetical list)
Topics in this section
About functions
About formulas
Using operators in formulas
Identifying text constants and special characters in formulas
Adding a new line to the results of a formula
Adding comments to a formula
Using a reserved word or symbol for a field or table name
Getting the contents of a repetition in a repeating field