Relative Strength Index (RSI)
Calculate the Relative Strength Index (RSI) indicator for a given price series.
The Relative Strength Index (RSI) is a momentum oscillator that measures the speed and change of price movements. It ranges from 0 to 100 and is used to identify overbought or oversold conditions in an asset’s price.
The formula is as follows:
\[\text{RSI} = 100 - (100 / (1 + \text{RS}))\]Also known as: RSI, momentum oscillator, overbought, oversold.
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Calculate the Relative Strength Index (RSI) in Python
The Relative Strength Index (RSI) is available in the Technicals module of the open-source Finance Toolkit. Install it with:
pip install financetoolkit -U
Then call get_relative_strength_index as shown below.
from financetoolkit import Toolkit
toolkit = Toolkit(tickers=["AAPL", "MSFT"])
toolkit.technicals.get_relative_strength_index()
Which returns:
| Date | AAPL | MSFT | Benchmark |
|---|---|---|---|
| 2026-06-18 | 39.0696 | 18.5547 | 44.8909 |
| 2026-06-22 | 42.1875 | 9.2816 | 42.6001 |
| 2026-06-23 | 30.4087 | 16.9139 | 37.6696 |
| 2026-06-24 | 32.6884 | 17.8779 | 39.5418 |
| 2026-06-25 | 22.9048 | 15.2531 | 38.4444 |
| 2026-06-26 | 33.4829 | 31.3248 | 44.9277 |
| 2026-06-29 | 35.3464 | 31.4673 | 50.9396 |
| 2026-06-30 | 49.0731 | 36.5041 | 54.943 |
| 2026-07-01 | 52.0534 | 44.4482 | 61.5893 |
| 2026-07-02 | 58.2929 | 50.0641 | 54.5966 |
Parameters
get_relative_strength_index accepts the following parameters:
- period (str, optional): The time period to consider for historical data. Can be “daily”, “weekly”, “quarterly”, or “yearly”. Defaults to “daily”.
- close_column (str, optional): The column name for closing prices in the historical data. Defaults to “Adj Close”.
- window (int, optional): The number of periods for RSI calculation. Defaults to 14.
- rounding (int | None, optional): The number of decimals to round the results to. Defaults to 4.
- growth (bool, optional): Whether to calculate the growth of the RSI. Defaults to False.
- lag (int | list[int], optional): The lag to use for the growth calculation.
- standardize (bool, optional): Whether to standardize (Z-Score) the result. When combined with growth=True, standardizes the growth values instead of the raw values. Defaults to False. Defaults to 1.
Related Momentum Indicators
The Technicals module page introduces the module, and the sidebar lists all of its functions.