Relative Strength measures a stock's price change over the last X months relative to the price change of a market index. It shows the relative outperformance or underperformance of the stock over that timeframe.
We calculate this value internally. It is calculated dividing the price change of a stock by the price change of the index for the same time period. e.g. A stock falling by 20% versus an index rising 20% would lead to a Relative strength calculation of 100 * ( 80/120 - 1) = -33%
For relative strength calculations, the benchmark index we use is the main index of the particular country or region as follows:
For any regions not covered above, we use the fallback index, which is the FTSE Global All Cap Index