RSI measures how fast a stock's price is moving up or down

RSI stands for Relative Strength Index. It is a number between 0 and 100 that tells you whether a stock has been rising or falling sharply over the last 14 days. A high RSI (above 70) means the stock has climbed steeply and may be due for a pullback. A low RSI (below 30) means it has fallen steeply and may be ready to bounce back up.

RSI does not predict what a stock will do next. It only describes what already happened. Many traders watch RSI because rapid moves in one direction often do reverse, but that pattern breaks often enough that RSI alone is not a reliable signal to buy or sell.

Think of RSI as a speedometer for price movement, not a map of where the price is headed. It answers "how fast is this stock moving?" not "will it go up tomorrow?"

Key Takeaways

  • RSI is a momentum indicator that ranges from 0 to 100 and measures how steeply a stock has risen or fallen over the past 14 trading days.
  • An RSI above 70 suggests a stock has moved up sharply and traders sometimes interpret this as a signal the price may pull back, though it often does not.
  • An RSI below 30 suggests a stock has fallen sharply and traders sometimes interpret this as a signal the price may bounce, though reversals are not may provide.
  • RSI is one tool among many and should not be used alone to decide whether to buy or sell a stock.

How RSI is calculated

RSI compares the average gain on up days to the average loss on down days over the last 14 trading days. If a stock went up more often than it went down, RSI climbs toward 100. If it went down more often than it went up, RSI falls toward 0.

You do not need to calculate RSI yourself. Every stock charting platform—Yahoo Finance, Fidelity, Charles Schwab, TradingView—displays RSI as a line graph below the price chart. The calculation is the same everywhere, so the number you see is consistent across platforms.

The 14-day period is the standard, but some traders change it to 7 days (more sensitive to recent moves) or 21 days (smoother, less reactive). Shorter periods make RSI swing between extremes more often; longer periods make it move more slowly.

What RSI above 70 and below 30 mean in practice

When RSI climbs above 70, traders call the stock overbought. This means the price has risen so fast that a correction downward becomes statistically more likely—but only slightly, and only over the next few days or weeks. An overbought stock can keep climbing for months if the company is genuinely performing well or if investor enthusiasm keeps building.

When RSI falls below 30, traders call the stock oversold. This means the price has fallen so fast that a bounce upward becomes statistically more likely. Again, this is not a may provide. A stock can keep falling if bad news keeps coming or if the market loses confidence in the company.

The trap many new traders fall into is treating RSI extremes as automatic buy or sell signals. They are not. RSI tells you the stock has moved sharply; it does not tell you why or whether the move is justified. A stock can be overbought and still go higher because the company's earnings are strong. A stock can be oversold and still go lower because the company is in real trouble.

Why traders watch RSI even though it is not reliable

RSI works often enough in calm markets that traders keep using it. When a stock has risen 20% in two weeks with no news, RSI above 70 often does precede a small pullback. When a stock has fallen 20% in two weeks with no news, RSI below 30 often does precede a small bounce. These patterns happen frequently enough to be worth noticing.

The problem is that news, earnings reports, and shifts in investor sentiment break these patterns constantly. A stock with RSI above 70 can announce a blockbuster earnings report and jump another 15%. A stock with RSI below 30 can announce a bankruptcy and fall another 30%. RSI does not account for these events because it only looks at price movement, not the reasons behind it.

Professional traders use RSI as one piece of information alongside price trends, volume, company fundamentals, and market conditions. They do not use it alone. Beginners often make the mistake of treating RSI as a standalone decision tool, which is why RSI-only trading strategies often fail.

RSI divergence: when RSI and price move in opposite directions

Some traders pay attention to divergence, which happens when the stock price reaches a new high but RSI does not. For example, a stock might climb to $150 (its highest price ever) but RSI only reaches 65 (lower than it was when the stock hit $140). This mismatch can signal that the upward momentum is weakening, even though the price is still rising.

Divergence is more reliable than RSI extremes alone, but it is still not a may provide. It works best when combined with other signals like volume (is the stock trading on heavy volume or light volume?) and price patterns (is the stock forming a recognizable chart pattern?).

How RSI compares to other momentum indicators

RSI is one of many momentum indicators. MACD (Moving Average Convergence Divergence) compares two moving averages and can signal when momentum is shifting. Stochastic is similar to RSI but uses a different calculation and often moves faster. Volume (how many shares traded) can confirm whether a price move has real conviction behind it.

None of these indicators predict the future reliably. They all describe what has already happened and suggest what might happen next based on historical patterns. Those patterns break when news, earnings, or market sentiment changes.

Many traders use two or three indicators together because they catch different things. RSI might show overbought conditions while volume shows declining interest, which together suggest a pullback is likely. But even that combination is not certain.

Common mistakes people make with RSI

The biggest mistake is treating RSI as a buy or sell signal by itself. Traders who buy every stock with RSI below 30 or sell every stock with RSI above 70 will lose money regularly because they are ignoring why the stock moved in the first place.

Another mistake is using RSI on very short time frames (hourly or minute-by-minute charts) where random price noise creates false signals constantly. RSI works better on daily or weekly charts where the signal is clearer.

A third mistake is ignoring the broader trend. A stock in a strong uptrend can stay overbought (RSI above 70) for weeks or months. Selling every time RSI hits 70 means you sell a winning stock early and miss most of the gains. The same applies in reverse: a stock in a downtrend can stay oversold for weeks.

Frequently Asked Questions

Is RSI above 70 a signal to sell?

Not automatically. RSI above 70 means the stock has risen sharply, which sometimes leads to a pullback, but it does not mean the stock will fall. Many strong stocks stay overbought for weeks. Selling based on RSI alone ignores whether the stock's price rise is justified by company performance or market conditions.

Can I use RSI to day trade?

RSI can be part of a day trading strategy, but it is less reliable on very short time frames because price noise creates false signals. Day traders who use RSI usually combine it with volume, price patterns, and support/resistance levels. Even then, day trading has high failure rates regardless of the indicators used.

What is the difference between RSI and moving averages?

RSI measures momentum (how fast the price is moving), while moving averages measure the direction of the trend. A moving average shows whether a stock is generally rising or falling over time. RSI shows whether that rise or fall is happening quickly or slowly. They answer different questions and work best together.

Does RSI work better on certain types of stocks?

RSI works more reliably on large, stable stocks that trade heavily because their price moves are less random. It works poorly on penny stocks or thinly traded stocks where a single large order can swing the price dramatically. It also works better in calm markets than in markets with major news or economic shocks.

Should I ignore RSI if I am a long-term investor?

Most long-term investors do not use RSI because they are not trying to time short-term price moves. If you are buying a stock to hold for years, whether RSI is 35 or 75 today does not matter much. RSI is mainly useful for traders trying to catch short-term bounces or pullbacks.