Add to a value: add

The add filter converts a value to a float and adds a specified amount to it. If the value cannot be converted to a number, it returns the default you provide instead of raising an error.

This is a convenient shorthand for arithmetic on sensorSensors return information about a thing, for instance the level of water in a tank. [Learn more] values. Instead of converting to a float first and then adding, you can do it in a single step. It is especially useful when you need to apply a fixed offset to a reading, such as adjusting a temperature sensor by a calibration value, adding a base cost to a calculated price, or shifting a time value. For multiplication, see multiply.

Usage

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

{{ states("sensor.temperature") | add(2.5) }}

24.0

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.

add(
    value: Any,
    amount: float,
    default: Any = _SENTINEL,
) -> float | Any

Function parameters

The following parameters can be provided to this filter.

Subtracting values

To subtract, pass a negative amount.

{{ states("sensor.temperature") | add(-5) }}

16.5

Using a default value

If the sensor might be unavailable, provide a default to prevent errors.

{{ states("sensor.temperature") | add(2.5, default=0) }}

24.0

Good to know

• There is no subtract filter. Pass a negative amount to subtract.
• The result is always a float, even when both inputs are integers.
• Without a default, a non-numeric input raises an error. Always pass a default when working with state values.

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.

Apply a calibration offset

Correct a temperature sensor reading by a known offset.

{{ states("sensor.outdoor_temperature") | add(-1.2) | round(1) }}

17.1

Calculate a total with a base fee

Add a fixed base cost to a calculated usage charge.

{{
  (states("sensor.energy_today") | float(0) * 0.25)
  | add(5.0) | round(2)
}}

8.47

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:

• Multiply a value: multiply - Multiplies a numeric value by a specified amount, with an optional default if conversion fails.

• 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.

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