# Calculated measures

A calculated measure combines two measures with an operator: **Plus**, **Minus**, **Multiplied by**, or **Divided by**. The most common use is a ratio, such as the average amount given per supporter, the cost per donation, or the share of supporters who gave again.

You can use calculated measures on any tile with measures, and they suit a headline figure on a [number tile](<https://help.apteco.com/en/orbit/dashboards/tiles/tile-types/number-tiles/index.md>) especially well. For what each part of a calculation can be, see [Measures](<https://help.apteco.com/en/orbit/dashboards/measures/index.md>).

> [!NOTE]
>
> A calculated measure in Orbit can differ slightly from the same calculation in FastStats, because FastStats rounds during the calculation. Orbit's value is calculated to a higher precision.

## Add a calculated measure

You add a calculated measure next to the tile's other measures.

To add a calculated measure:

1. With your dashboard in edit mode, expand the **option menu** on your tile and select **Edit Tile**.
2. Under **Measure** or **Measures**, select **Calculated Measure**, next to **\+ Add Measure**.
3. In each part of the calculation, select **\+ Add Measure** and choose a measure. Between them, choose the operator, such as **Plus**.
4. To show the result as a percentage, choose **Percentage** from **Display As**.
5. Select **Apply**, then **Save** the dashboard.

For the measure's other settings, such as its title and decimal places, see [Measure settings](<https://help.apteco.com/en/orbit/dashboards/tiles/tile-editor/#measure-settings>).

## Combine measures from different tables

When the two measures in a calculation come from different tables, how Orbit joins those tables decides the result. You don't need to create or change any tables, but you do need to choose the join that answers your question. The left table is the one your calculation's values come from, and you choose it with the tile's **Select Via** setting.

The three joins are:

- **Left join**: All the relevant records from the left table, and only the related records from the right table
- **Inner join**: Only the records from each table that are related to records in the other
- **Right join**: All the relevant records from the right table, and only the related records from the left table

For example, with **Households** as the left table and **Loyalty Members** as the right table, a left join includes every household, while an inner join includes only households with loyalty members.

### Left join

To include every record from the left table, set the tile's **Select Via** to the left table, then turn on **Return All Values** in **Data Settings**. See [Change the Select Via table](<https://help.apteco.com/en/orbit/dashboards/filtering/resolve-tables/#change-the-select-via-table>).

> [!NOTE]
>
> Only let viewers filter on the left table. Filters on other tables stop the calculation giving the result you expect.

### Inner join

To include only related records, add two [tile filters](<https://help.apteco.com/en/orbit/dashboards/filtering/tile-filters/index.md>) to the tile: one that selects every record in the left table, and one that selects every record in the right table. For example, filter on every category of a variable from **Households**, such as **State**, and every category of a variable from **Loyalty Members**, such as **Title**.

### Right join

A right join is what you get by default, with no changes to the tile.

> [!NOTE]
>
> Only let viewers filter on the right table. Filters on other tables stop the calculation giving the result you expect.