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

# Realised volatility

> How much the underlying actually moved, on the same scale as implied vol.

Realised volatility (RV) measures how much the underlying index actually moved over a trailing window,
annualised so that it sits on the same scale as implied volatility.

Each hourly row gives RV over the `lookback_days` that end at that hour. `lookback_days=30` means each point
looks back 30 days.

## Lookbacks

`lookback_days` takes `1`, `7`, `14`, `30`, `60`, `90`, `180`, `270` or `365`.

Choose the lookback to match the implied tenor you're comparing against:

| Implied tenor | Matching RV lookback |
| - | - |
| `1w` | `7` |
| `2w` | `14` |
| `1m` | `30` |
| `2m` | `60` |
| `3m` | `90` |
| `6m` | `180` |
| `9m` | `270` |
| `1y` | `365` |

> [!NOTE]
>
> Realised vol looks **back** and implied vol looks **forward**. At time *t*, 1-month IV prices the next 30
> days, while 30-day RV measures the last 30. To check how well implied vol forecast what happened, compare IV
> at *t* with RV at *t + 30 days*. See [Implied vs realised](https://docs.sandmark.com/guides/iv-vs-rv.md).

## Fields

**RV** `number`

Annualised realised volatility, decimal. `0.3519` is 35.19 vol.

**LOOKBACK\_DAYS** `number`

The trailing window in days. `LOOKBACK_LABEL` is the same window as a tenor label (`30` → `1m`).

**DATETIME** `string`

The hour the window ends, UTC.


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