What Is the RSI Indicator?
- Above 70: traditionally considered overbought
- Below 30: traditionally considered oversold
- Above 50: generally indicates stronger bullish momentum
- Below 50: generally indicates stronger bearish momentum
- Default setting: 14 periods
- Divergence: price and RSI moving differently can warn that momentum is changing
Technical analysis becomes much more useful when you stop asking an indicator to predict the future and instead ask it to describe what the market is doing right now.
That distinction is especially important with the Relative Strength Index. RSI is one of the most popular technical indicators in trading, but it is also one of the easiest to misuse.
A trader sees RSI hit 70 and immediately thinks, "the stock is overbought — sell." Another sees RSI below 30 and assumes the stock has to bounce.
Neither conclusion is necessarily true.
RSI becomes much more powerful when you understand what it actually measures: momentum. From there, RSI can help you evaluate trend strength, identify momentum shifts, spot divergences and improve the timing of entries and exits.
How Does the RSI Indicator Work?
The Relative Strength Index was developed by technical analyst J. Welles Wilder Jr. and introduced in 1978.
RSI compares the magnitude of recent gains with the magnitude of recent losses. The result is converted into an oscillator that moves between 0 and 100.
Think of RSI as a momentum gauge.
- A rising RSI indicates that recent upward price movements are becoming stronger relative to downward movements.
- A falling RSI indicates that recent downward movements are becoming stronger relative to upward movements.
The standard RSI uses 14 periods. On a daily chart, that normally means 14 trading days. On an hourly chart, it means 14 hourly candles. On a 5-minute chart, it means 14 five-minute candles.
That makes RSI usable across stocks, ETFs, indexes, forex and cryptocurrencies, as well as across many different trading timeframes.
How Is RSI Calculated?
You do not need to calculate RSI manually because virtually every modern charting platform does it automatically. However, understanding the formula helps explain what the indicator is actually measuring.
RS = Average Gain / Average Loss
Suppose a stock has experienced much larger average gains than average losses over the measurement period. RS rises, causing RSI to move toward 100.
If recent losses dominate recent gains, RSI moves toward 0.
The important takeaway is that RSI isn't comparing a stock with another stock or with the S&P 500. Despite the name Relative Strength Index, it is measuring the strength of the security's own recent gains versus its recent losses.
What Do RSI 70 and 30 Mean?
The traditional RSI interpretation uses two major levels:
- RSI above 70 = overbought
- RSI below 30 = oversold
These levels tell you that price momentum has reached an extreme relative to its recent history.
But there is a major mistake traders make here:
A stock experiencing exceptionally strong buying pressure can become overbought because its trend is extremely strong. Selling simply because RSI reaches 70 can therefore cause you to exit one of the strongest stocks in the market.
The opposite can happen during a major decline. A stock can reach RSI 30, continue falling, hit RSI 25 and remain oversold while price falls much further.
Why RSI Overbought Does NOT Automatically Mean Sell
This is arguably the single most important concept to understand about RSI.
Imagine a stock breaks out of a six-month consolidation after unexpectedly strong earnings. Buyers flood into the stock and RSI jumps from 55 to 74.
A simplistic interpretation says:
"RSI is above 70. Sell."
But RSI may be above 70 precisely because a powerful new trend has started. If price continues higher, RSI could remain between 65 and 85 for days or even weeks.
Instead of treating 70 as an automatic sell signal, ask:
- Is the stock in a strong uptrend?
- Did price just break resistance?
- Is trading volume confirming the move?
- Is trend strength increasing?
- Is RSI diverging from price?
RSI should provide context, not dictate a trade by itself.
Real RSI Example: Tesla Overbought and Oversold
The Tesla chart below demonstrates why RSI extremes need context. The stock bounced after RSI reached an oversold condition and later experienced a pullback after RSI became severely overbought.
But notice something important: the larger price trend did not automatically reverse every time RSI reached an extreme. Price eventually returned to its broader direction.
This is why I prefer using RSI extremes as an alert to investigate the setup rather than as an automatic buy or sell command.
The RSI 50 Level: An Underrated Signal
Traders spend so much time watching 70 and 30 that they often ignore the middle of the indicator.
The 50 level can be extremely useful for understanding momentum.
- RSI above 50: recent gains are dominating recent losses.
- RSI below 50: recent losses are dominating recent gains.
That doesn't mean crossing 50 predicts the next candle. Instead, it provides a quick way to evaluate which side currently has greater momentum.
For example, suppose a stock is above its moving averages, price structure is making higher highs and higher lows, and RSI repeatedly pulls back toward 45-50 before moving higher again.
That behavior can be more useful than waiting for RSI to become oversold at 30. The stock may never reach 30 because the underlying uptrend is too strong.
RSI Bull and Bear Market Ranges
Another more advanced way to use RSI is to stop assuming that every market should oscillate evenly between 30 and 70.
Strong trends can shift the entire RSI range.
During a healthy uptrend, RSI may repeatedly find support around the 40-50 area and spend much of its time above 50.
During a persistent downtrend, RSI may repeatedly struggle around the 50-60 area and spend much of its time below 50.
This gives traders another way of thinking about RSI: the range itself can tell you something about the underlying trend.
If you want to measure the strength of that trend independently, RSI pairs particularly well with the ADX trend-strength indicator.
RSI Divergence: One of the Most Useful RSI Signals
One of my favorite uses of RSI is divergence.
Divergence occurs when price and RSI stop confirming each other.
Bullish RSI Divergence
Bullish divergence occurs when:
- Price makes a lower low, but
- RSI makes a higher low.
Price is technically weaker, but downside momentum is no longer confirming that weakness.
That can be an early warning that selling pressure is exhausting itself. This is personally one of the RSI setups I find most interesting because it can identify potential bounces before they become obvious on the price chart.
Bearish RSI Divergence
Bearish divergence is the opposite:
- Price makes a higher high, but
- RSI makes a lower high.
Price is still rising, but momentum is failing to confirm the new high. That can warn that the move is losing strength.
However, divergence is a warning, not a reversal guarantee. Price can continue trending for a surprisingly long time while divergence develops.
I am particularly cautious about using bearish RSI divergence as a standalone reason to short a stock. Shorting introduces its own risks, and strong stocks can continue climbing despite weakening momentum.
If you're considering short trades, read How to Short Stocks before treating an RSI divergence as a trade by itself.
Real Example: Bearish RSI Divergence
The chart below shows an example where price and RSI stopped confirming each other. Price continued pushing higher while RSI momentum weakened.
RSI Failure Swings
A less commonly discussed RSI technique is the failure swing. Unlike ordinary divergence, this setup focuses primarily on RSI itself.
Bullish Failure Swing
A simplified bullish failure swing occurs when RSI:
- Falls into oversold territory.
- Rebounds.
- Pulls back but remains above its previous RSI low.
- Breaks above the previous RSI swing high.
That sequence suggests momentum has transitioned from extreme weakness toward increasing strength.
Bearish Failure Swing
The bearish version occurs when RSI reaches an elevated level, pulls back, fails to make a stronger momentum high, and then breaks its previous RSI low.
Failure swings can help traders avoid the simplistic approach of buying merely because RSI touched 30 or selling merely because it touched 70.
Best RSI Settings: 7, 14 or 21?
The traditional setting developed by Wilder is 14 periods, and it remains the standard starting point.
But there is nothing magical about 14.
| RSI Setting | Behavior | Potential Use |
|---|---|---|
| 7 RSI | Fast, sensitive, more extreme readings | Short-term trading |
| 14 RSI | Balanced/default | General-purpose analysis |
| 21 RSI | Slower and smoother | Swing/longer-term analysis |
Shorter RSI settings respond more rapidly but create more noise. Longer settings smooth the oscillator but react more slowly.
The best setting is therefore the one that works with your market, timeframe and trading system, not the setting somebody on social media claims is universally optimal.
How I Would Build an RSI Trading Strategy
RSI becomes far more useful when combined with independent information rather than stacking several indicators that all measure essentially the same thing.
A basic framework might look like this:
- Determine the trend. Is price structurally trending up, down or sideways?
- Measure trend strength. Use something such as ADX.
- Evaluate momentum. Is RSI above or below 50? Is momentum strengthening?
- Look for an RSI setup. Extreme reading, divergence, range support or failure swing.
- Check price structure. Support, resistance, breakouts and previous highs/lows matter.
- Confirm participation. Check whether volume supports the move.
- Define risk before entering. Know where the setup becomes invalid.
The important part is that RSI becomes one component of a system rather than the entire system.
If you have never formally built one, read my guide on how to create a stock trading system.
RSI + ADX: Momentum Meets Trend Strength
RSI and ADX make a logical combination because they answer different questions.
- RSI: What is happening to momentum?
- ADX: How strong is the trend?
For example, an RSI reading above 70 while ADX is rising strongly can be very different from an RSI reading above 70 while the trend is deteriorating.
The first may represent strong trend momentum. The second may deserve more caution.
Read my complete ADX Indicator Guide to understand how trend strength can complement RSI.
RSI + Moving Averages
Another useful combination is RSI with moving averages.
A moving average can establish the broader trend while RSI measures the momentum occurring inside that trend.
For example, instead of automatically buying every RSI reading below 30, a trader might focus on RSI pullbacks occurring while price remains within an established bullish trend.
You can learn the differences between moving-average types in EMA vs SMA: Which Moving Average Is Better?.
For a more advanced trend visualization, see my EMA Cloud trading strategy.
RSI vs Stochastic Oscillator
RSI and the Stochastic Oscillator are both momentum oscillators, but they are not identical.
RSI focuses on the magnitude of recent gains relative to recent losses. The Stochastic Oscillator instead looks at where the current closing price sits relative to the recent high-low range.
Both can identify momentum extremes, but because they are calculated differently, they can behave differently under the same market conditions.
See my guide to the Stochastic Oscillator for a deeper comparison.
The Biggest RSI Mistakes
Most problems with RSI come from interpretation rather than the indicator itself.
- Automatically selling at RSI 70. Strong trends can remain overbought.
- Automatically buying at RSI 30. Weak stocks can remain oversold while continuing to collapse.
- Ignoring the larger trend. RSI behaves differently in trending and ranging markets.
- Treating divergence as guaranteed. Divergence can persist before price reverses.
- Optimizing settings without backtesting. A setting that looks perfect on one chart may fail elsewhere.
- Using RSI alone. Momentum without price structure, volume and risk management gives you an incomplete picture.
This is part of a larger problem traders have with technical analysis: indicators are tools, not crystal balls.
I've discussed that problem in more detail in What's Wrong With Technical Indicators?
Backtest RSI Instead of Guessing
If you want to know whether RSI actually provides an edge, don't rely on a few beautiful historical examples. Turn your idea into objective rules and test it.
For example:
- What happens when RSI crosses back above 30?
- Does requiring price above the 200-day moving average improve the result?
- Does ADX improve the signal?
- Do RSI divergences work better on daily charts than intraday charts?
- Does RSI 20 produce better entries than RSI 30 for a particular stock?
TrendSpider can be used to automate technical analysis and test rule-based trading ideas rather than manually scrolling through hundreds of charts.
If you're interested in taking systematic trading further, Hands-On Trading With Python covers building and testing quantitative strategies programmatically.
RSI Frequently Asked Questions
What does RSI mean?
RSI stands for Relative Strength Index. It is a momentum oscillator that compares the magnitude of recent price gains with recent price losses and expresses the result on a scale from 0 to 100.
What is a good RSI to buy?
There is no universal RSI value that means "buy." RSI below 30 is traditionally considered oversold, but a stock can remain below 30 while continuing to fall. Trend, price structure, volume and other confirmation should be considered.
What does RSI above 70 mean?
RSI above 70 traditionally indicates an overbought condition. It means upward momentum has been unusually strong relative to recent history. It does not necessarily mean the stock is about to fall.
What does RSI below 30 mean?
RSI below 30 traditionally indicates an oversold condition. Downward momentum has reached an extreme, but that alone does not guarantee a rebound.
What does RSI 50 mean?
The 50 level acts as a useful momentum midpoint. Sustained readings above 50 generally indicate stronger positive momentum, while sustained readings below 50 indicate stronger negative momentum.
What is the best RSI setting?
The standard RSI setting is 14 periods. Shorter settings such as 7 react faster but create more noise, while longer settings such as 21 are smoother but slower. The appropriate setting depends on the market, timeframe and strategy.
Is RSI a leading indicator?
RSI can sometimes warn that momentum is changing before the change becomes obvious in price, particularly through divergence. However, RSI does not reliably predict future prices and should not be treated as a standalone forecasting tool.
Conclusion: RSI Is More Than Overbought and Oversold
The Relative Strength Index is far more useful than the basic "70 = sell, 30 = buy" interpretation suggests.
RSI can help you evaluate:
- Momentum direction
- Momentum strength
- Overbought and oversold conditions
- Bullish and bearish divergence
- Failure swings
- Bullish and bearish RSI ranges
- Changes in the character of a trend
Of these, I particularly like watching for situations where price makes a lower low while RSI makes a higher low. That loss of downside momentum can produce some very interesting reversal setups.
But no RSI signal should be considered guaranteed. The better approach is to combine momentum with trend, price structure, volume and a defined risk-management system.
Learn the behavior of the indicator, test it against actual market data and then decide where RSI belongs within your own trading system.