---
id: "T:cAlgo.API.Indicators.BollingerBands"
kind: "interface"
namespace: "cAlgo.API.Indicators"
url: "https://help.ctrader.com/ctrader-algo/references/Indicators/BollingerBands/"
---

> Documentation index for agents: https://help.ctrader.com/ctrader-algo/llms.txt · machine index: https://help.ctrader.com/ctrader-algo/api.json

# BollingerBands (interface)

Bollinger Bands are used to confirm signals. The bands indicate overbought and oversold levels relative to a moving average.

Environments: Desktop supported · CLI supported · Cloud supported.

## Definition

```csharp
public interface BollingerBands
```

## Remarks

Bollinger bands widen in volatile market periods, and contract during less volatile periods. Tightening of the bands is often used a signal that there will shortly be a sharp increase in market volatility.

## Examples

C#:

```csharp
var bollingerBands = Indicators.BollingerBands(Bars.ClosePrices, 20, 2, MovingAverageType.Simple);
Print("Top: {0}, Main: {1}, Bottom: {2}", bollingerBands.Top.LastValue, bollingerBands.Main.LastValue, bollingerBands.Bottom.LastValue);
```

Python:

```python
bollingerBands = api.Indicators.BollingerBands(api.Bars.ClosePrices, 20, 2, MovingAverageType.Simple)
api.Print(f"Top: {bollingerBands.Top.LastValue}, Main: {bollingerBands.Main.LastValue}, Bottom: {bollingerBands.Bottom.LastValue}")
```

C#:

```csharp
using cAlgo.API;
using cAlgo.API.Indicators;

namespace cAlgo.Robots
{
    // This sample cBot shows how to use the Bollinger Bands indicator
    public partial class BollingerBandsSample : Robot
    {
        private double _volumeInUnits;

        private BollingerBands _bollingerBands;

        public Position[] BotPositions
        {
            get
            {
                return Positions.FindAll(Label);
            }
        }

        protected override void OnStart()
        {
            _volumeInUnits = Symbol.QuantityToVolumeInUnits(VolumeInLots);

            _bollingerBands = Indicators.BollingerBands(Source, 14, 2, MovingAverageType.Exponential);
        }

        protected override void OnBar()
        {
            if (Bars.LowPrices.Last(1) <= _bollingerBands.Bottom.Last(1) && Bars.LowPrices.Last(2) > _bollingerBands.Bottom.Last(2))
            {
                ClosePositions(TradeType.Sell);

                ExecuteMarketOrder(TradeType.Buy, SymbolName, _volumeInUnits, Label);
            }
            else if (Bars.HighPrices.Last(1) >= _bollingerBands.Top.Last(1) && Bars.HighPrices.Last(2) < _bollingerBands.Top.Last(2))
            {
                ClosePositions(TradeType.Buy);

                ExecuteMarketOrder(TradeType.Sell, SymbolName, _volumeInUnits, Label);
            }
        }

        private void ClosePositions(TradeType tradeType)
        {
            foreach (var position in BotPositions)
            {
                if (position.TradeType != tradeType) continue;

                ClosePosition(position);
            }
        }
    }
}
```

Python:

```python
import clr

clr.AddReference("cAlgo.API")

# Import cAlgo API types
from cAlgo.API import *

# Import trading wrapper functions
from robot_wrapper import *

class BollingerBandsSample():
    def on_start(self):
        self.volumeInUnits = api.Symbol.QuantityToVolumeInUnits(api.VolumeInLots)
        self.bollingerBands = api.Indicators.BollingerBands(api.Source, 14, 2, MovingAverageType.Exponential)

    def on_bar_closed(self):
        if api.Bars.LowPrices.Last(0) <= self.bollingerBands.Bottom.Last(0) and api.Bars.LowPrices.Last(1) > self.bollingerBands.Bottom.Last(1):
            self.close_positions(TradeType.Sell)
            api.ExecuteMarketOrder(TradeType.Buy, api.SymbolName, self.volumeInUnits, api.Label)
        elif api.Bars.HighPrices.Last(0) >= self.bollingerBands.Top.Last(0) and api.Bars.HighPrices.Last(1) < self.bollingerBands.Top.Last(1):
            self.close_positions(TradeType.Buy)
            api.ExecuteMarketOrder(TradeType.Sell, api.SymbolName, self.volumeInUnits, api.Label)

    def get_bot_positions(self):
        return api.Positions.FindAll(api.Label)

    def close_positions(self, tradeType):
        for position in self.get_bot_positions():
            if position.TradeType != tradeType:
                continue
            api.ClosePosition(position)
```

config.json:

```json
{
  "AccessRights": "None",
  "TimeZone": "UTC",
  "Parameters": [
    {
      "Name": "VolumeInLots",
      "DisplayName": "Volume (Lots)",
      "Type": "Double",
      "DefaultValue": 0.01
    },
    {
      "Name": "Label",
      "Type": "String",
      "DefaultValue": "Sample"
    },
    {
      "Name": "Source",
      "Type": "DataSeries"
    }
  ]
}
```

## Properties

- `IndicatorDataSeries Bottom {get;}` — Lower Bollinger Band. [details](https://help.ctrader.com/ctrader-algo/references/Indicators/BollingerBands/Bottom/index.md)
- `IndicatorDataSeries Main {get;}` — Moving Average (Middle Bollinger Band). [details](https://help.ctrader.com/ctrader-algo/references/Indicators/BollingerBands/Main/index.md)
- `IndicatorDataSeries Top {get;}` — Upper Bollinger Band. [details](https://help.ctrader.com/ctrader-algo/references/Indicators/BollingerBands/Top/index.md)

## Inherited members

- `ChartIndicator AddToChart()` (from StandardIndicator) [details](https://help.ctrader.com/ctrader-algo/references/General/StandardIndicator/AddToChart/index.md)
- `Symbol Symbol {get;}` (from StandardIndicator) [details](https://help.ctrader.com/ctrader-algo/references/General/StandardIndicator/Symbol/index.md)
- `TimeFrame TimeFrame {get;}` (from StandardIndicator) [details](https://help.ctrader.com/ctrader-algo/references/General/StandardIndicator/TimeFrame/index.md)
- `Bars Bars {get;}` (from StandardIndicator) [details](https://help.ctrader.com/ctrader-algo/references/General/StandardIndicator/Bars/index.md)