Test if value is numeric: is_number

The is_number template function tests whether a value can be converted to a valid, finite floating-point number. It returns true if the value is numeric and false otherwise. Values like infinity and NaN are not considered numbers and return false.

This is a safety check you should use before performing math on values that might not be numeric. 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 in Home Assistant can be unavailable, unknown, or other non-numeric strings at any time. Trying to do math on these values without checking first causes errors. By testing with is_number first, you can branch your logic to handle numeric and non-numeric cases separately. It is also useful as a template test in {% if %} blocks.

Usage

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

{{ is_number("21.5") }}

true

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

true

{% if states("sensor.temperature") is is_number %}
  It is a number!
{% endif %}

It is a number!

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 default are required.

is_number(
    value: Any,
) -> bool

Function parameters

The following parameters can be provided to this function.

What counts as a number

The function attempts to convert the value to a float. If the conversion succeeds and the result is a finite number (not infinity or NaN), it returns true.

{{ is_number(42) }}
{{ is_number("21.5") }}
{{ is_number("unavailable") }}
{{ is_number("inf") }}

true
true
false
false

Good to know

• Returns false for unavailable, unknown, infinity, and NaN, which catches common unsafe cases for math.
• Booleans pass this test because Python treats True and False as 1 and 0.
• Numeric strings like "21.5" pass. This checks convertibility, not the current type.

Try it yourself

Ready to test this? Open Developer 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.

Guard a calculation

Only perform math if the sensor value is actually a number.

{% if states("sensor.power_usage") | is_number %}
  {{ states("sensor.power_usage") | float * 0.25 }}
{% else %}
  Sensor is not reporting a number
{% endif %}

62.5

Filter a list to only numeric values

When working with multiple sensorsSensors return information about a thing, for instance the level of water in a tank. [Learn more], filter out any that are not reporting numbers before calculating an average.

{{
  ["21.5", "unavailable", "19.8", "unknown"]
  | select("is_number")
  | map("float")
  | list
  | average
}}

20.65

Use in an automation condition

Only proceed if the sensor is reporting a valid number.

condition:
  - condition: template
    value_template: >
      {{ states("sensor.wind_speed") | is_number }}

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 float: float - Converts a value to a floating-point number, with an optional default if conversion fails.

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

• Check if entity has a value: has_value - Tests if an entity exists and has a valid state (not unavailable or unknown).

• Get the type of a value: typeof - Returns the type name of a value as a string.