---
url: /indicators/fcb.md
description: >-
  Created by Edward William Dreiss, Fractal Chaos Bands outline high and low
  price channels to depict broad less-chaotic price movements.  FCB is a
  channelized depiction of Williams Fractal.
package: FacioQuo.Stock.Indicators
docs_version: v3
canonical: https://dotnet.stockindicators.dev/indicators/fcb
generated: 2026-09-30T04:41:06.055Z
commit: ae1f432eaa0b03ae9f39e032c69434b557efa4a2
---

# Fractal Chaos Bands (FCB)

Created by Edward William Dreiss, Fractal Chaos Bands outline high and low price channels to depict broad less-chaotic price movements.  FCB is a channelized depiction of [Williams Fractal](/indicators/fractal.md).
[\[Discuss\] 💬](https://github.com/facioquo/stock-indicators-dotnet/discussions/347 "Community discussion about this indicator")

```csharp
// C# usage syntax
IReadOnlyList<FcbResult> results =
  bars.ToFcb(windowSpan);
```

## Parameters

| param | type | description |
| ----- | ---- | ----------- |
| `windowSpan` | *`int`* | Fractal evaluation window span width (`S`).  Must be at least 2.  Default is 2. |

The total evaluation window size is `2×S+1`, representing `±S` from the evaluation date.  See [Williams Fractal](/indicators/fractal.md) for more information about Fractals and `windowSpan`.

### Historical price bars requirements

You must have at least `2×S+1` periods of `bars` to cover the warmup periods; however, more is typically provided since this is a chartable candlestick pattern.

`bars` is a collection of generic `TBar` historical price bars.  It should have a consistent frequency (day, hour, minute, etc).  See [the Guide](/guide/getting-started.md#historical-bars) for more information.

## Response

```csharp
IReadOnlyList<FcbResult>
```

* This method returns a time series of all available indicator values for the `bars` provided.
* It always returns the same number of elements as there are in the historical price bars.
* It does not return a single incremental indicator value.
* The periods before the first fractal are `null` since they cannot be calculated.

> [!WARNING]
> **️🖌️ Repaint warning**
>
> Fractal Chaos Bands are based on [Williams Fractal](/indicators/fractal.md), which uses future bars.  This indicator will never identify bands in the last `S` periods of `bars` since fractals are retroactively identified.

### `FcbResult`

| property | type | description |
| -------- | ---- | ----------- |
| `Timestamp` | *`DateTime`* | Date from evaluated `TBar` |
| `UpperBand` | *`decimal`* | FCB upper band |
| `LowerBand` | *`decimal`* | FCB lower band |

### Utilities

* [.Condense()](/utilities/results.md#condense)
* [.Find(lookupDate)](/utilities/results.md#find-by-date)
* [.RemoveWarmupPeriods()](/utilities/results.md#remove-warmup-periods)
* [.RemoveWarmupPeriods(removePeriods)](/utilities/results.md#remove-warmup-periods)

See [Utilities and helpers](/utilities.md) for more information.

## Chaining

This indicator is not chain-enabled and must be generated from `bars`.  It **cannot** be used for further processing by other chain-enabled indicators.

See [Chaining indicators](/guide/chaining.md) for more.

## Streaming

Use the buffer-style `List<T>` when you need incremental calculations without a hub:

```csharp
FcbList fcbList = new(windowSpan);

foreach (IBar bar in bars)  // simulating stream
{
  fcbList.Add(bar);
}

// based on `ICollection<FcbResult>`
IReadOnlyList<FcbResult> results = fcbList;
```

Subscribe to a `BarHub` for advanced streaming scenarios:

```csharp
BarHub barHub = new();
FcbHub observer = barHub.ToFcbHub(windowSpan);

foreach (IBar bar in bars)  // simulating stream
{
  barHub.Add(bar);
}

IReadOnlyList<FcbResult> results = observer.Results;
```

See [Buffer lists](/guide/styles/buffer.md) and [Stream hubs](/guide/styles/stream.md) for full usage guides.