Power Automate Expressions

Expressions unlock the full power of Power Automate. This guide teaches you the logic, the editor, and every major function category, with real examples you can start using today.

What are expressions?

In Power Automate, most action inputs accept either a dynamic value (a piece of data from a previous step) or a static value (text you type in). Expressions are a third option that lets you compute a value using a formula, combining functions, dynamic data, and constants.

Think of expressions as the formula bar in Excel, but for your flow. Instead of clicking a cell reference, you reference flow data. Instead of =UPPER(A1), you write toUpper(triggerBody()?['Title']).

Every expression is evaluated at runtime, meaning Power Automate runs the formula and replaces it with the computed result before passing that value to the action.

The expression editor

To write an expression, click inside any action input field. A small lightning bolt icon or the dynamic content panel will appear. Switch to the Expression tab in the dynamic content panel. You will see a text box where you type your formula.

When you click OK, the expression is saved. In the designer, it shows as a blue pill with the function name visible. To edit it, just click the pill again.

String functions

String functions let you build, clean, slice, and search text values. These are used in almost every real-world flow: formatting names, building email subjects, extracting substrings from codes, and more.

concat: Joining strings together

concat(value1, value2, ...) joins any number of strings into one. You can pass as many arguments as you need.

toUpper and toLower

Normalise case for comparisons or display. Always lowercase before comparing. Otherwise "London" and "london" are treated as different values.

trim: Removing whitespace

User-entered data often has accidental leading or trailing spaces. trim() removes them.

replace: Substituting text

replace(text, findText, replaceWith) replaces every occurrence of a substring. Useful for sanitising filenames, stripping characters, or formatting codes.

substring: Extracting part of a string

substring(text, startIndex, length) extracts a portion. Index starts at 0. The third parameter is the length: how many characters to take.

indexOf and lastIndexOf

indexOf(text, searchText) returns the position of the first match (0-based). Returns -1 if not found. Combine with substring to extract dynamic parts.

startsWith and endsWith

Return true or false. Great inside if() conditions.

split: Turning a string into an array

split(text, delimiter) breaks a string into an array of substrings. The result can be used in an Apply to Each loop.

length: Counting characters

Logical functions

Logical functions evaluate conditions and return values based on whether conditions are true or false. They are the backbone of dynamic flow behaviour.

if: The ternary operator

if(condition, valueIfTrue, valueIfFalse) is the most important logical function. It evaluates a condition and returns one of two values. There is no built-in IF action in cloud flows for expressions. This is your tool.

equals, not, greater, greaterOrEquals, less, lessOrEquals

These comparison functions all return true or false and are typically used inside if() or as condition expressions.

and / or

Combine multiple conditions. and(condition1, condition2) is true only if both are true. or(condition1, condition2) is true if either is true.

contains: Checking for a value

Works on strings, arrays, and objects. For strings it checks for a substring. For arrays it checks if the value exists in the array.

Date and Time functions

Dates in Power Automate are ISO 8601 strings (like 2026-05-17T09:00:00Z). All date functions work with this format.

utcNow: The current timestamp

utcNow() returns the current UTC date and time as an ISO 8601 string. It takes an optional format pattern.

formatDateTime: Formatting a date for display

formatDateTime(timestamp, format) converts any ISO 8601 date string to a human-friendly format. The format string uses standard .NET date tokens.

addDays, addHours, addMinutes, addSeconds, addMonths

Add (or subtract using negative numbers) to a timestamp. Essential for calculating due dates, expiry times, and scheduling offsets.

convertTimeZone

Converts a UTC timestamp to a local time zone. Important when displaying times to users in specific regions.

dayOfWeek, dayOfMonth, month, year

Extract parts of a date as integers.

Math functions

Math functions operate on numbers. They are straightforward but easy to misuse when dealing with strings that look like numbers. Always convert first.

add, sub, mul, div, mod

min and max: Smallest and largest value

abs, power, sqrt

Collection functions

Collection functions work on arrays and objects. These are extremely powerful when combined with the array actions (see the Array Actions guide), because they let you query and transform arrays directly in expressions.

length: Count items in an array

first and last

Get the first or last item from an array.

take and skip

take(array, count) returns the first N items. skip(array, count) skips the first N and returns the rest. Combine them to paginate or slice arrays.

union and intersection

union() merges arrays removing duplicates. intersection() returns only items present in all arrays.

createArray: Building an array inline

Useful when you need to pass a list of values without a prior step.

contains: Checking membership

join: Converting an array to a string

Turns an array into a single string with a separator. Great for building comma-separated lists.

empty: Checking if an array is empty

Conversion functions

Data from triggers and API responses often comes as strings even when it represents numbers or booleans. Conversion functions cast between types to avoid runtime errors.

int and float: Parsing numbers from strings

string: Converting values to text

bool: Parsing boolean values

json: Parsing a JSON string into an object

When an HTTP response body comes back as a string rather than parsed JSON, use json() to convert it so you can access its properties with ?['key'].

array: Wrapping a single value in an array

base64 and decodeBase64

uriComponent and uriComponentToBinary

Encode strings for use in URLs. Escapes spaces and special characters.

Workflow context functions

These functions let you access data from the flow's own context: the trigger, previous actions, variables, loop items, and flow metadata. They are the most used category in real flows.

triggerBody() and triggerOutputs()

triggerBody() returns the body of whatever triggered the flow. For a SharePoint trigger this is the list item. For a Forms trigger this is the response. For a manual trigger this is the user-supplied input.

triggerBody()?['Title']          // SharePoint item Title
triggerBody()?['EmailAddress']   // Forms question answer
triggerOutputs()?['headers']?['x-ms-trigger-type']  // trigger metadata

body('ActionName') and outputs('ActionName')

Access the output of a specific previous action by its internal name. Use the name as shown in the action title bar (spaces become underscores).

body('Get_item')?['Title']
body('Send_an_HTTP_request_to_SharePoint')?['body']
outputs('Get_item')?['headers']

items('ActionName'): Current loop item

Inside an Apply to Each loop, items('Apply_to_each') refers to the current item in the iteration. Use ?['FieldName'] to access its properties.

items('Apply_to_each')?['Title']
items('Apply_to_each')?['AssignedTo']?['Email']

variables('variableName')

Reads the current value of a flow variable. Variables must first be initialised with the Initialize Variable action.

parameters('parameterName')

Reads a solution-level parameter. Useful for configuration values that change between environments (dev, test, production).

workflow(): Flow metadata

Returns metadata about the current flow run including its name, ID, run ID, and environment.

Common patterns

Null-safe access with coalesce

When a field might be null or missing, wrap it with coalesce() to provide a fallback value. Without this, a null field will crash your expression.

Checking for null explicitly

Building a filename from fields + date

Calculating business day offset

Converting a SharePoint person field to email

triggerBody()?['AssignedTo']?['Email']
body('Get_item')?['Author']?['Email']

Reading a choice field value

triggerBody()?['Priority']?['Value']    // Choice field text
triggerBody()?['Priority']?['Id']       // Choice field numeric ID

Getting array length for a condition

Hello Alice Johnson