> For the complete documentation index, see [llms.txt](https://help.modelreef.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.modelreef.io/syntax/formula-syntax/formula-output-preview.md).

# Formula Output Preview

This article explains **formula output preview** in the Model Reef Formula editor.

You will learn:

* What the preview shows.
* How to use it to validate your formulas.
* How it fits into the wider modelling workflow.

The preview gives a quick visual check before you commit formula changes.

***

## What the preview displays

The formula preview usually shows:

* A basic chart or small table of the resulting time series.
* Key metadata about the series, such as its type or approximate range.
* Any warnings related to extreme values or unusual patterns.

It is not a full report, but a focused view to help verify correctness.

***

## When the preview updates

The preview updates when:

* The expression is syntactically valid.
* All references resolve to known variables or drivers.

As you edit the formula:

* The preview updates automatically after each valid change.
* If the formula becomes invalid, the preview may disappear until you fix the error.

This encourages an iterative edit-and-check workflow.

***

## Using the preview to validate logic

You can use the preview to check:

* Whether the general shape of the series matches expectations (for example growth, seasonality or step changes).
* Whether the magnitude of values appears sensible.
* Whether there are unexpected spikes or drops.

If the preview does not match your mental model of the series, revisit the formula or the drivers it uses.

***

## Limitations of the preview

The preview is not intended to:

* Replace full inspection of P\&L, Balance Sheet and Cashflow.
* Show every detail of the series across long horizons.
* Provide multi-scenario comparisons.

After saving a formula, you should still confirm its impact in core financial statements and key dashboards.

***

## Workflow with previews

{% stepper %}
{% step %}

### Open the Formula editor

Open the Formula editor for a variable.
{% endstep %}

{% step %}

### Compose or adjust the formula

Compose or modify the expression you want to use.
{% endstep %}

{% step %}

### Watch the preview

Watch the preview to ensure the resulting series looks right.
{% endstep %}

{% step %}

### Save the formula

Save the formula when you are happy with it.
{% endstep %}

{% step %}

### Confirm broader impact

Check financial statements and dashboards in the scenario to confirm the broader impact.
{% endstep %}
{% endstepper %}

Using the preview as an early check helps catch issues before they ripple through the model.

***

## Related articles

* [Understanding the Interface](/syntax/understanding-the-interface.md)
* [Units & Display](/syntax/variables-syntax/units-and-display.md)
* [COGS Mapping](/help/financial-outputs-and-valuation/cogs-mapping.md)
* [Build an Equity Valuation Model (FCFE)](/how-tos/valuation/build-an-equity-valuation-model-fcfe.md)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://help.modelreef.io/syntax/formula-syntax/formula-output-preview.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.