Clamp (constrain) a value: clamp

The clamp template function constrains a value to lie within a given range. If the value is below the minimum it returns the minimum; if it is above the maximum it returns the maximum; otherwise it returns the value unchanged. The range is inclusive on both ends.

This is useful whenever you need to ensure a sensorSensors return information about a thing, for instance the level of water in a tank. [Learn more] value stays within safe bounds before using it in an automationAutomations in Home Assistant allow you to automatically respond to things that happen in and around your home. [Learn more]. For example, you could clamp a brightness percentage to a range your light supports, limit a thermostat setpoint to a safe temperature range, or ensure a volume level never exceeds a certain maximum.

Usage

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

{{ clamp(150, 0, 100) }}

100.0

{{ 150 | clamp(0, 100) }}

100.0

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.

clamp(
    value: Any,
    min_value: Any,
    max_value: Any,
) -> float

Function parameters

The following parameters can be provided to this function.

Good to know

• Both bounds are inclusive, so a value equal to the minimum or maximum is returned unchanged.
• The result is always a float, even when all inputs are integers.
• If min_value is greater than max_value, the result will always be min_value.

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.

Limiting a thermostat setpoint

Ensure a calculated setpoint stays within a safe range.

{% set desired = states("sensor.target_temperature") | float %}
{{ clamp(desired, 16, 28) }}

22.0

Clamping brightness

Keep a brightness value within the 0-255 range that a light expects.

{% set raw = states("sensor.ambient_light") | float * 2.5 %}
{{ clamp(raw, 0, 255) }}

255.0

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:

• Wrap a value cyclically: wrap - Wraps a value cyclically within a range.

• Remap a value between ranges: remap - Remaps a value from one numeric range to another, with optional stepping and edge handling.

• Minimum value: min - Returns the smallest value from a list of values.

• Maximum value: max - Returns the largest value from a list of values.