Relative Strength Index

What is RSI?

RSI measures momentum - is a stock overbought (too high, due for drop) or oversold (too low, due for bounce)? Ranges from 0-100. Above 70 = overbought. Below 30 = oversold.

Think of it like this

Think of a rubber band. Stretch it too far (RSI > 70) and it wants to snap back. Let it go slack (RSI < 30) and it wants to tighten. RSI measures how stretched the price is.

Formula

RSI = 100 - (100 / (1 + RS))
  • RS: Average Gain / Average Loss
  • Period: Usually 14 days

Why it matters

  • Identifies potential reversal points
  • Shows momentum strength
  • Helps time entries and exits
  • Works in trending and ranging markets

What's a good value?

< 30
Oversold
Potentially due for bounce
30-50
Bearish
Downward momentum
50-70
Bullish
Upward momentum
> 70
Overbought
Potentially due for pullback

Real-world example

GameStop RSI hit 95 in January 2021 - extremely overbought, crashed soon after. March 2020 crash: many stocks RSI < 20 - extreme oversold, then rebounded strongly.

Things to watch out for

  • Can stay overbought/oversold in strong trends
  • False signals in choppy markets
  • Use with other indicators for confirmation
  • Different timeframes give different readings

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