> ## Documentation Index
> Fetch the complete documentation index at: https://alphacastio.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Apply Formula

> Apply one formula to many columns at once, producing a new suffixed column for each.

The **Apply Formula** step runs a single formula across several columns in one go. Where [Calculate Variable](/steps/calculate-variable) creates one new column from a formula you write, this step applies the same formula to each column you select and produces one new column per input.

## Configuration

| Field   | Description                                                        |
| ------- | ------------------------------------------------------------------ |
| Formula | The formula to apply. It operates on each selected column in turn. |
| Columns | The columns to apply it to.                                        |
| Suffix  | Appended to each column name to name the result.                   |

Output columns are named `{original column} - {suffix}`. So applying a formula with the suffix `real` to `Exports` and `Imports` produces `Exports - real` and `Imports - real`, leaving the originals in place.

<Note>
  The formula uses the same grammar as [Calculate Variable](/steps/calculate-variable) — see the [formula reference](/steps/formula-reference) for every operator and function.
</Note>

<Warning>
  The step fails if the formula, the suffix, or the column selection is missing. All three are required.
</Warning>

<Tip>
  Reach for this when you would otherwise add the same Calculate Variable step five times with only the column name changing — deflating several nominal series, or converting a group of columns to an index.
</Tip>

## Next steps

<CardGroup cols={2}>
  <Card title="Formula reference" icon="function" href="/steps/formula-reference">
    Every operator and function available.
  </Card>

  <Card title="Calculate variable" icon="function" href="/steps/calculate-variable">
    Write a formula producing a single new column.
  </Card>
</CardGroup>