# Dimensions and measures

> Define the attributes you group and filter by, and the aggregations you measure, in dbt-compatible YAML

*[View this page in the Flax docs](https://flax-analytics.com/docs/modeling/dimensions-and-measures)*

Dimensions and measures are the queryable fields of a model. This page shows how to define them, with examples grounded in the Flax spec. They live under the `flax:` key of a dbt model, so the file stays a valid dbt schema file.

## Dimensions

A **dimension** is an attribute you group or filter by — an order's status, a customer's country, or the date an order was placed. Each dimension needs a `name`, a `type`, and a `sql` expression. In `sql`, `${column}` refers to a column on this model.

```yaml
flax:
  dimensions:
    - name: status
      type: string
      sql: ${status}
    - name: order_date
      type: time
      time_grains: [day, week, month, quarter, year]
      sql: ${created_at}
```

Dimension types are `string`, `number`, `boolean`, and `time`. A `time` dimension may declare `time_grains` — the buckets (day, week, month, quarter, year) a viewer can roll up to. Add a human-friendly `label`, a `description`, and set `hidden: true` to keep a field out of the explore picker while still using it in expressions.

## Measures

A **measure** is an aggregation over rows. Each needs a `name` and a `type`; most types also take a `sql` expression naming the column to aggregate.

```yaml
flax:
  measures:
    - name: order_count
      label: Number of orders
      type: count
      sql: "*"
    - name: total_revenue
      label: Total revenue
      type: sum
      sql: ${amount}
    - name: completed_revenue
      label: Completed revenue
      type: sum
      sql: ${amount}
      filters:
        - ${status} = 'complete'
```

Supported measure types: `count`, `count_distinct`, `sum`, `average`, `min`, `max`, `median`, `percentile`, and `number` (a raw expression, not aggregated). A `percentile` measure takes a `percentile:` value between 0 and 1 (e.g. `0.25` for Q1).

### Filtered measures

The optional `filters` list holds SQL boolean expressions that are AND-ed into the aggregation. `completed_revenue` above sums `amount` only for rows where `status = 'complete'`, so you can define revenue variants without new columns.

## Formats and labels

Use `label` to control how a field appears in the UI, and `description` to document intent — both surface in the explore experience and the AI assistant's context. Display formatting (currency, decimals, percentages) is applied at visualization time; see [Formatting and theming](/docs/visualizations/formatting-and-theming).

> [!TIP]
> Prefer defining a filtered measure over asking every analyst to add the same `WHERE` clause. Define once, reuse everywhere.

## Next steps

- [Relationships and joins](/docs/modeling/relationships-and-joins) — query across models.
- [Semantic YAML reference](/docs/modeling/semantic-yaml-reference) — every field and its constraints.
- [SQL compilation](/docs/modeling/sql-compilation) — how these compile per dialect.