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 = 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

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 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.

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.