Convert to float: float

The float template function converts a value to a floating-point number. If the value cannot be converted, it returns the default you provide instead of raising an error. This “forgiving” behavior makes it safe to use with sensorSensors return information about a thing, for instance the level of water in a tank. [Learn more] values that might sometimes be unavailable or unknown.

In Home Assistant, all entityAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more] states are stored as strings, even when they represent numbers. This means that states("sensor.temperature") returns 21.5 (a string), not 21.5 (a number). Before you can do any math with a state value, such as comparing it to a threshold, adding values together, or using it in a calculation, you must convert it to a number first. The float function (or filter) is the standard way to do this.

Usage

Here’s how to use this template function. Copy any example and adjust it to your setup.

{{ float("21.5") }}

21.5

{{ states("sensor.temperature") | float }}

21.5

Function signature

The signature is a technical summary of this template function. It shows the name of the function, the values (called parameters) it accepts, and what type of data each parameter expects (for example, a piece of text or a number).

Function parameters that have a = with a value after them are optional. If you leave them out, the default value shown is used automatically.

Function parameters without a = are usually required. A few optional parameters have no default value, so the signature shows them without a = as well. To check whether a parameter is required, look at the parameter list below the signature. Each parameter is marked as Required or Optional.

The most common optional parameter without a default value is default. The default parameter sets the value a function returns when the function can’t produce a result, for example, when float gets text that isn’t a number. If you leave out default, there is no fallback value, so most functions raise an error and the template fails. The parameter list of each function says what happens. If you set default, the function returns your value instead.

round(
    value: Any,
    precision: int = 0,
    method: str = "common",
    default: Any,
) -> float | int | Any

float(
    value: Any,
    default: Any,
) -> float | Any

Function parameters

The following parameters can be provided to this function.

Using a default value

Since sensorSensors return information about a thing, for instance the level of water in a tank. [Learn more] states can be unavailable or unknown, always provide a default to prevent your templateA template is an automation definition that can include variables for the action or data from the trigger values. This allows automations to generate dynamic actions. [Learn more] from breaking.

{{ states("sensor.temperature") | float(0) }}

21.5

If the sensor state were unavailable, this would return 0 instead of raising an error.

Why conversion is needed

All entity states in Home Assistant are strings. Without conversion, comparisons and math produce unexpected results or errors:

{{ states("sensor.temperature") | float > 25 }}

false

Good to know

• Without a default, conversion failures raise an error that can break your template. Always pass a default when reading from entity states.
• The default is returned when the input is None, unavailable, unknown, or any value that cannot be converted.
• The default does not have to be a number. Passing a string like "unknown" is valid when you want a readable fallback.

Try it yourself

Ready to test this? Open Settings > Tools > Template, paste the example into the Template editor, and watch the result update on the right. Edit the values to see how the function adapts to your own entitiesAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more].

More examples

Real scenarios where this function comes up in automations and templates. Copy any example and adapt it to your setup.

Calculate a temperature difference

Calculate the difference between indoor and outdoor temperatures.

{{
  (states("sensor.indoor_temperature") | float(0))
  - (states("sensor.outdoor_temperature") | float(0))
}}

5.3

Use in an automation triggerA trigger is the part of an automation that makes the automation start when something specific happens, for example, when the sun sets, a door opens, or a button is pressed. [Learn more]

Trigger when the power usage exceeds a threshold. The float filter ensures the string state is compared as a number.

trigger:
  - trigger: template
    value_template: >
      {{ states("sensor.power_usage") | float(0) > 3000 }}

Convert with a fallback in a notification

Send a notificationYou can use notifications to send messages, pictures, and more, to devices. [Learn more] that includes a sensor value, using a readable fallback if the sensor is unavailable.

action:
  - action: notify.mobile
    data:
      message: >
        The humidity is
        {{ states("sensor.humidity") | float("unknown") }}%

Still stuck?

The Home Assistant community is quick to help: join Discord for real-time chat, post on the community forum with your template and expected result, or share on our subreddit /r/homeassistant.

Related template functions

These functions work well alongside this one:

• Convert to integer: int - Converts a value to an integer, with an optional default if conversion fails.

• Test if value is numeric: is_number - Tests whether a value can be converted to a finite number.

• Round a number: round - Rounds a numeric value to a specified number of decimal places using various rounding methods.

• Convert to boolean: bool - Converts a value to a boolean (true/false), with an optional default if conversion fails.