2026.10.4
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Get length of a collection: length

The length filter returns the number of items in a collection. For lists, it returns the number of elements. For strings, it returns the number of characters. For dictionaries, it returns the number of keys. It is also available under the alias count.

This is one of the most commonly used filters when working with 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] collections. You will frequently use it to count how many lights are on, how many doors are open, how many sensorsSensors return information about a thing, for instance the level of water in a tank. [Learn more] are above a threshold, or how many devicesA device is a model representing a physical or logical unit that contains entities. are in a particular area. It typically appears at the end of a filter chain after select, selectattr, or expand.

Usage

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

As a filter 
{{ [1, 2, 3, 4, 5] | length }}
Result (integerA whole number without decimal places, like 1, 42, or -5. Used for counts, indices, and whole values.) 
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.

How to read a signature

Here is the signature of the round filter as an example:

round(
    value: Any,
    precision: int = 0,
    method: str = "common",
    default: Any,
) -> float | int | Any
  • round is the name of the function.
  • Between the parentheses are the parameters. Each parameter has a name, followed by a colon and the type of value the parameter expects. The type only tells you what kind of value to pass. For default: Any, you pass a value of any type, such as 0 or "unknown", not the word Any.
  • = 0 and = "common" are default values. You can leave out precision and method, and round uses these default values.
  • default has no =, but the parameter list marks default as optional. If you leave out default and round gets a value that isn’t a number, round raises an error.
  • -> shows the type of value the function returns.
  • Inside a signature, | means “or”. This function returns a decimal number, a whole number, or the value you passed as default.

round is a filter, so the first parameter, value, is the value before the |. For example, {{ 3.14159 | round(2) }} returns 3.14.

The types you’ll see most often:

  • str: text, such as "hello"
  • int: a whole number, such as 5
  • float: a decimal number, such as 3.14
  • bool: true or false
  • list: a list of values, such as [1, 2, 3]. list[str] is a list of texts.
  • dict: a set of keys and values, such as {"name": "Kitchen"}
  • datetime and timedelta: a date and time, and a duration. For details, refer to Dates and times.
  • None: no value
  • Any: any type of value

Some signatures use special forms:

  • *args means you can pass any number of values, separated by commas. For example, average(1, 2, 3).
  • value | name(...) means the function is a filter. The value before the | is passed to the filter as its first parameter. Some filter signatures, like the round example, show this value as the first parameter between the parentheses instead.
length(
    value: Sized,
) -> int

Function parameters

The following parameters can be provided to this filter.

value any Required

The list, string, or dictionary to measure. Any object that supports len() is accepted.

The count alias

The count filter is an alias for length. They behave identically.

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] 
{{ ["a", "b", "c"] | count }}
Result (integerA whole number without decimal places, like 1, 42, or -5. Used for counts, indices, and whole values.) 
3

Good to know

  • Cannot count generators directly. Add | list after select, map, or selectattr first.
  • For strings, it counts characters, not words or bytes.

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.

Count how many lights are on

Count the number of lights currently in the “on” state.

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] 
{{
  expand("light.home_lights")
  | selectattr("state", "eq", "on")
  | list
  | length
}}
Result (integerA whole number without decimal places, like 1, 42, or -5. Used for counts, indices, and whole values.) 
5

Count open doors

Count how many door sensors report an “on” (open) state.

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] 
{{
  expand("binary_sensor.door_sensors")
  | selectattr("state", "eq", "on")
  | list
  | count
}}
Result (integerA whole number without decimal places, like 1, 42, or -5. Used for counts, indices, and whole values.) 
2

Get the number of attributes on an entity

Count how many attributes a particular entity has.

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] 
{{ states.sensor.weather.attributes | length }}
Result (integerA whole number without decimal places, like 1, 42, or -5. Used for counts, indices, and whole values.) 
8

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.

Tip

AI assistants like ChatGPT or Claude can also explain or fix templates when you describe what you want in plain language.

Related template functions

These functions work well alongside this one: