Add & Calculate a New Field

This tutorial covers creating a new attribute field and calculating its values in one step with the Calculate Field tool.

Included in this tutorial:

• Accessing the Calculate Field tool

• Calculate Field tool parameters

• Adding and Calculating a new field

• A ratio of two existing fields

• Copying values with a new data type

Software version in examples: ArcGIS Pro 3.6.0

Tutorial Data: The tutorial includes demonstration with sample data available here.

Credits: L. Meisterlin (2026)

Related Tutorials:

• Adding and Calculating Fields in an Attribute Table

Accessing the Calculate Field tool

You can find the Calculate Field tool in the Geoprocessing Pane by clicking through Toolboxes > Data Management > Calculate Field or by using the Geoprocessing Pane’s search box.

---

Calculate Field Tool parameters

View fullsize

the Calculate Field tool dialogue box

1. Input Table: The table in which which contains (or will contain) the field to be calculated.

2. Field Name (Existing or New): 

• If an Existing Field: choose its name from the dropdown menu.

• If a New Field: type its name into the text box

3. Field Type: This option only appears if the Field Name (above) is new. Specify the data type of the new field.

4. Expression Parameters

• Expression Type: Choose the method of your expression. The default is Python.

• Expression:  Construct the expression (which will calculate the field’s values) within the Expression parameter (it is the text box following the equal sign = ). 

• Fields: A list of fields in the Input Table is provided to help build your expression. You can insert a field as a variable by double clicking its name.

• Helpers: A list of “helper functions” is provided for building your expression. 

• Code Block: You can optionally use the code block if your expression calls upon a custom function. 

• More helpers and operators: The drop down and the operator buttons are also available to minimize typing into the expression text box (to reduce typing errors).

---

Adding and Calculating a New Field (two examples)

The following section demonstrates two examples of adding and calculating a new field with the Calculate Field tool: calculating a ratio from two existing fields and creating a new field with integer values from numerical characters in an existing text field.

Calculating a New Field with a Ratio

View fullsize

calculating a new field with a ratio

Calculating a New Integer Field from Numerical Text Values

View fullsize

calculating a new integer field