Relative Strength Index (RSI)
Just like a runner's heart rate monitor tracks when someone is gasping for air or catching their breath, RSI acts as a dashboard gauge showing whether the stock market is running too hot or completely exhausted.
Definition The Relative Strength Index (RSI) is a technical indicator that measures the speed and strength of recent price changes on a scale from 0 to 100. It helps investors quickly spot whether an asset is overbought (bought too aggressively and potentially expensive) or oversold (dumped too heavily and potentially undervalued).
A Speedometer for Price Momentum
A sprinter running at full speed will eventually run out of breath and need to slow down. Stock prices behave similarly: when a price surges without taking a breather, buyers eventually exhaust their cash and sellers step in to take profits. On the flip side, when a price plummets off a cliff, bargain hunters eventually appear, deciding that the shares have become too cheap to ignore.
The Relative Strength Index translates this tug-of-war between buyers and sellers into a clean, objective number. By default, it tracks price movements over the past 14 days, comparing the average size of gains on up days against the average size of losses on down days.
If an asset climbed every single day, RSI would approach 100. If it fell every single day, RSI would drop near 0. By putting price action on a 0 to 100 scale, RSI lets you check how hot the market's engine is running.
Reading the Signals: The 70 and 30 Thresholds
When reading RSI, traders pay close attention to two standard threshold lines: 70 and 30. When RSI climbs above 70, the asset enters overbought territory. This indicates that excessive buying enthusiasm pushed the price up rapidly, potentially creating short-term froth.
Conversely, when RSI dips below 30, the asset enters oversold territory. This suggests that panic selling drove the price down so fast that it may now trade below fair value.
Because of this, many investors watch for RSI to cross above 70 and roll back down as a cue that momentum is cooling off and it may be time to take profits. Similarly, when RSI drops below 30 and curls back up, bargain seekers treat it as a potential signal that a bottom has formed.
To Be Precise: Crossing 70 Doesn't Mean an Instant Crash
Crossing above 70 does not mean a stock will instantly crash the next morning. When a company benefits from game-changing news or blowout earnings, its RSI can stay pinned above 70 or 80 for days, or even weeks, while the stock continues to rally.
Traders refer to this as an indicator getting pegged to the ceiling. If you rush to sell simply because RSI passed 70, you risk stepping off a powerful bull run way too early.
Likewise, a company facing severe structural trouble can see its RSI sink below 30 and stay depressed as prices keep making lower lows. That is why smart investors never use RSI in isolationโthey combine it with company fundamentals, trading volume, and other technical tools to see the complete picture.
๐ค Common misconceptions
When RSI tops 70, the stock price will drop immediately.
In powerful uptrends, RSI can remain above 70 for extended periods while prices keep climbing. An RSI above 70 simply flags an overheated condition, not an automatic sell trigger.
๐งบ Where you meet it
RSI evaluates recent buying and selling momentum on a 0 to 100 scale to help investors spot overbought and oversold market conditions.