Specify Calculation dialog box
This dialog box appears so that you can build a formula for a calculation or calculated field.
1. If necessary, for Evaluate this calculation from the context of, choose a table from the list.
Setting the context for a calculation is only necessary when you're creating a calculation field in a source table that has two or more occurrences in the relationships graph. The choice you make may affect the calculation results, particularly if your calculation will include fields in related tables.
For more information on the use of context in calculations, see Choosing the evaluation context for a calculation field.
2. Build a formula for your calculation using field references, operators, constant values, and functions.
In the calculation pane, click where you want the item to appear, then:
To add
Do this
A reference to a field
Do one of the following:
Begin typing the field’s table, choose the table from the list, begin typing the field name, then choose the field name from the list the appears.
In the fields pane, double-click the field name. To display field names from a different table, choose the table from the tables list.
An operator or an exponent
Do one of the following:
Type an operator.
Click an operator in the list to the right of the calculation pane.
A constant value
Type the value.
A function
Do one of the following:
Begin typing the function name, then choose a function name from the list that appears.
In the functions pane, double-click the function.
In the calculation pane, replace the placeholder parameter with a value or expression.
3. Specify calculation options for the field.
Do this
Set the field type of the result
Choose a data type for Calculation result is <value>.
Choose the correct type for the result you want. See About choosing a field type.
Make a calculated field repeating
For Number of repetitions, type the number of repetitions. See Defining repeating fields.
Prevent calculation if all referenced fields are empty
Select Do not evaluate if all referenced fields are empty.
When enabled, FileMaker Pro does not evaluate a calculation if all fields used by the calculation are empty. This typically improves performance.
Important  To avoid confusion when using dates in FileMaker Pro, always define calculation formulas to enter four-digit years. See Conversion of dates with two-digit years.
4. To select indexing and storage options for the field, click Storage Options, choose options in the Storage Options dialog box, then click OK.
See Defining field indexing options and Defining global fields (fields with global storage).
5. Click OK.
To show or hide the functions pane, click Show/hide functions pane button in the Specify Calculation dialog box.
To filter the list of fields or functions in the fields pane or the functions pane, type the field name or function name in the search box.
To change the way fields or functions are displayed in the fields pane or the functions pane, click .
Related topics 
About functions
About formulas
Adding comments to a formula
Defining calculation fields
Defining automatic data entry
Defining field validation
Defining field indexing options