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

# Normalize Body Fat Percentage

> Divides body_fat_percentage values stored 100× too large back to the correct percentage, affecting Samsung and Google Health Connect data ingested before PR #917.

**Script:** `scripts/data_migrations/normalize_body_fat_percentage.py`

## Problem

`ImportService` (`backend/app/services/apple/healthkit/import_service.py`) is the shared ingestion path for Apple, Samsung, and Google SDK payloads. It unconditionally applied a ratio→percent `×100` conversion to `body_fat_percentage`.

That conversion is correct only for Apple HealthKit, where `HKUnit.percent()` returns a `0..1` ratio. Android Health Connect (Samsung, Google) reports `BodyFatRecord.percentage.value` already in percent, so those values were stored \~100× too large — e.g. an actual `30.4%` was saved as `3040`.

PR [#917](https://github.com/the-momentum/open-wearables/pull/917) fixed the ingestion path by gating the `×100` on `provider == "apple"`. This script corrects rows already in the database.

## What it does

Finds every `data_point_series` row for `body_fat_percentage` where `value > 100` and divides the value by `100`. Valid body fat percentages are always in the 0–100 range, so this threshold cleanly separates affected rows from correct ones without touching Apple or other provider data.

The `data_point_series_archive` table is not touched — archive rows are historical snapshots and do not feed live queries.

## Usage

```bash theme={null}
# Preview affected rows (recommended first step)
docker compose exec app uv run python scripts/data_migrations/normalize_body_fat_percentage.py --dry-run

# Apply corrections
docker compose exec app uv run python scripts/data_migrations/normalize_body_fat_percentage.py
```

## Options

| Flag        | Description                                                             |
| ----------- | ----------------------------------------------------------------------- |
| `--dry-run` | Print affected rows with current and corrected values. No changes made. |

## Dry run output

```
Rows with body_fat_percentage > 100: 3

ID                                     Provider        Current  Corrected  Recorded at
-----------------------------------------------------------------------------------------------
0c6b9ec9-...                           samsung        3040.000     30.400  2025-11-07 10:17:52+00:00
a052baa2-...                           samsung        2200.000     22.000  2025-11-05 10:17:52+00:00
632dffc6-...                           google         1850.000     18.500  2025-11-06 10:17:52+00:00

Dry run — no changes made.
```

## Related

* PR [#917](https://github.com/the-momentum/open-wearables/pull/917) — the ingestion fix that prevents new incorrect rows from being created.