RSI Indicator Explained - Finding Overbought and Oversold Stocks

The Relative Strength Index (RSI) is a momentum indicator that measures how quickly a stock is rising or falling. It's one of the most popular technical indicators because it's easy to interpret and useful across all timeframes.

What Is RSI?

RSI stands for Relative Strength Index. It measures the magnitude of recent price changes to evaluate overbought or oversold conditions.

RSI ranges from 0 to 100:

• RSI > 70: Overbought (stock has risen steeply)
• RSI < 30: Oversold (stock has fallen steeply)
• RSI 40–60: Neutral (no strong momentum either way)

RSI is calculated using an average of up-closes and down-closes over the last 14 periods (14 days, 14 hours, etc., depending on your timeframe).

RSI Formula (simplified): RSI = 100 − (100 ÷ (1 + RS))

Where RS = average gain over 14 periods ÷ average loss over 14 periods.

In plain English: RSI compares recent up-moves to recent down-moves. If a stock has been rising, RSI climbs. If it's been falling, RSI drops.

Interpreting RSI Levels

RSI Range	Signal	Typical Action
70–100	Overbought	Consider taking profits, tighten stops, be cautious on new longs
60–70	Strong uptrend	Still bullish; buying pressure remains
50–60	Mild uptrend	Momentum is fading; watch for reversals
40–50	Mild downtrend	Selling pressure building
30–40	Strong downtrend	Still bearish; selling remains
0–30	Oversold	Consider buying pullbacks, watch for bounces

Example: Apple (AAPL) in October 2024

Imagine AAPL rallied from $200 to $235 over three weeks. RSI climbed from 40 to 82—overbought territory.

This doesn't mean AAPL will crash. It means the stock has risen steeply and might pullback. Traders might:

• Take some profits (lock in gains)
• Tighten stops (protect against a reversal)
• Wait for RSI to drop back below 70 before buying more (avoid chasing)

Over the next few days, AAPL pulls back to $228. RSI drops to 65. This is healthier—the momentum has cooled but the uptrend remains intact (RSI > 60, price above moving averages).

Overbought ≠ Sell Signal

The most common mistake: assuming RSI > 70 means sell immediately.

In a strong uptrend, RSI can stay above 70 for weeks or months. During the tech bull market of 2020–2021, Nasdaq and mega-cap tech stocks spent 60%+ of the time above RSI 70. Shorting every overbought reading would have been catastrophic.

Overbought means momentum has been strong, not that a reversal is imminent.

Use overbought as a warning to be cautious, not as a sell signal. Combine it with other factors:

• Is the stock above its 50-day MA? (Still in uptrend)
• Is volume high or declining? (High volume supports momentum)
• Is there support below? (Where would you get stopped out?)

Oversold ≠ Buy Signal

The reverse mistake: assuming RSI < 30 means buy immediately.

In a strong downtrend, RSI can stay below 30 for weeks. Oversold in a downtrend often leads to more losses, not bounces.

In March 2020 (COVID crash), the S&P 500 fell from 3,300 to 2,200. RSI hit 20 (extremely oversold). Traders who bought the "oversold" S&P 500 at 2,500 watched it fall further to 2,200 before eventually recovering.

Oversold can mean the selling pressure is overwhelming, not that a bounce is coming.

Use oversold as a sign to watch for reversals, not as an automatic buy. Combine it with:

• Support levels (where do technicians expect a bounce?)
• Volume (is selling volume declining, suggesting the selling pressure is easing?)
• Macroeconomic conditions (is the broader market in crisis or just consolidating?)

RSI Divergence

An RSI divergence is when price makes a new high (or low) but RSI doesn't.

Bullish divergence: Price makes a new low, but RSI makes a higher low. This suggests selling pressure is fading; a bounce might come.

Bearish divergence: Price makes a new high, but RSI makes a lower high. This suggests buying pressure is fading; a pullback might come.

Example: A Stock Rising to a New High

NVDA rallies from $100 to $125 (a new high). RSI reached 80 during this rally.

Over the next week, NVDA continues rallying to $128 (a new all-time high). But RSI only reaches 76 (lower than the 80 it was at $125).

This bearish divergence suggests momentum is weakening even though the stock is higher. A pullback might follow. The stock rises but the "velocity" of the rise is slowing.

Divergences are useful but not foolproof. They signal a potential reversal, not a guarantee. Wait for confirmation (a close below support, a break below the 50-day MA) before acting.

RSI in Trending vs. Ranging Markets

In trending markets (strong up or down), RSI can stay extreme (>70 or <30) for long periods, giving false signals if you treat it mechanically.

In ranging markets (sideways, bouncing between two levels), RSI oscillates between 30 and 70, and overbought/oversold reversals are more reliable.

This is the key limitation: RSI works well in ranges but poorly in strong trends. Always check the larger-timeframe trend before using RSI.

How Professional Traders Use RSI

Trend confirmation: RSI > 60 confirms an uptrend is healthy; RSI < 40 confirms a downtrend is healthy.

Support and resistance levels: In a downtrend, the 30 level on RSI acts like support. Each time RSI bounces off 30, it suggests a relief bounce. In an uptrend, the 70 level acts like resistance.

With other indicators: RSI + moving averages + price action + volume. For example, "Price bounced off the 50-day MA AND RSI < 30 AND volume increasing = strong buy signal."

Divergence signals: RSI divergence + price at resistance = watch for a reversal.

Exit rules: "Exit if RSI rises above 80 and price breaks above resistance" (trend exhaustion). "Exit if RSI falls below 20 and price breaks below support" (trend reversal).

Real Example: Tesla (TSLA) in 2024

TSLA rallied from $150 to $280 over six months. RSI was mostly above 60, often >70.

A trader who shorted every time TSLA's RSI hit 70 would have been crushed—TSLA rallied 87% despite being overbought most of the time.

A better approach: "TSLA is above the 50-day MA and RSI > 60 = strong uptrend. Don't short. Wait for either a break below the 50-day MA OR a close below recent support OR a dramatic RSI drop. Those are confirmation signals."

When TSLA eventually cooled (late 2024), RSI fell below 60, then below 50, signaling momentum was fading. A trader holding from $150 to $280 could have taken profits when RSI broke below 60—a more reliable exit than a mechanical "RSI > 70 = sell" rule.

Common Mistakes

Trading only RSI: Too many false signals. Use it as confirmation, not a standalone system.

Shorting overbought in an uptrend: This is the fastest way to lose money. Uptrends have prolonged overbought periods.

Buying oversold in a downtrend: Similarly, downtrends have prolonged oversold periods. Oversold doesn't mean "about to reverse."

Using too short a period: RSI is typically 14 periods. Using RSI(5) makes it too sensitive and whippy; using RSI(21) makes it less responsive. Stick with 14 unless you have a reason to change.

Ignoring the larger trend: A bearish divergence in an uptrend is weaker than a bearish divergence in a downtrend. Check the daily chart if you're trading on 5-minute charts; context matters.

Key Takeaways

• RSI ranges from 0 to 100 and measures momentum.
• RSI > 70 is overbought (caution, not a sell signal); RSI < 30 is oversold (caution, not a buy signal).
• RSI > 60 confirms an uptrend is healthy; RSI < 40 confirms a downtrend is healthy.
• RSI divergence (price at new high but RSI lower) can signal a reversal.
• RSI works best in ranging markets; it gives false signals in strong trends.
• Combine RSI with moving averages, support/resistance, and volume for reliable signals.
• In an uptrend, wait for RSI to break below 60 or 50 combined with support breaks before exiting.
• In a downtrend, wait for RSI to break above 40 or 50 combined with resistance breaks before exiting.
• Use RSI as one tool in a toolkit, not as the sole basis for trades.