The Relative Strength Index, or RSI indicator, helps you understand the momentum behind a price move. It compares recent gains with recent losses and converts that information into a number between 0 and 100.
You will often hear that an RSI above 70 means “overbought” and below 30 means “oversold”. Those levels are useful, but they do not automatically tell you to buy or sell. Understanding what sits behind the number can make RSI much more useful.
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What is the Relative Strength Index?
The Relative Strength Index (RSI) is a momentum oscillator used in technical analysis to measure the speed and magnitude of recent price movements. It moves between 0 and 100 and shows how recent upward price movements compare with recent downward movements.
RSI measures price momentum, not valuation. An RSI of 70 or above does not mean a stock is fundamentally overvalued, just as an RSI of 30 or below does not mean it is fundamentally undervalued. A 14-period RSI is commonly used, with each period corresponding to the timeframe of the chart. For example, a daily chart uses daily periods, while an hourly chart uses hourly periods.
Source: NISM, Reading the Market’s Language, 8 April 2026; NSE, Technical Analysis Essentials, updated 14 August 2026.
Also Read: MACD indicator: Meaning, Calculation and How to Use It?
Key Takeaways
- The Relative Strength Index (RSI) is a momentum indicator that measures the speed and magnitude of recent price movements on a scale of 0 to 100.
- RSI is commonly calculated over 14 periods, although the setting can be adjusted depending on the timeframe being analysed.
- Readings of 70 or above are conventionally considered overbought, while readings of 30 or below are considered oversold, but neither is an automatic reversal signal.
- RSI divergence occurs when price and RSI move differently and can indicate that the momentum behind the current price trend is weakening.
- RSI is more useful when read alongside price trends, support and resistance, volume or other indicators rather than used on its own.
Key features of RSI
Here are the key features that explain how RSI measures and reflects price momentum:
- Bounded scale: RSI always moves between 0 and 100.
- Momentum measurement: It compares the strength of recent gains with recent losses.
- Overbought and oversold zones: Readings of 70 or above and 30 or below are conventionally watched for unusually strong upward or downward momentum.
- Centreline: The 50 level can help indicate whether recent gains or losses are stronger on average.
- Divergence: Differences between price movement and RSI movement can highlight weakening momentum.
Relative Strength Index formula
The RSI calculation compares average gains with average losses over a selected number of periods, conventionally 14.
First, calculate relative strength:
RS = Average gain / Average loss
Then calculate RSI:
RSI = 100 − [100 / (1 + RS)]
For the traditional RSI calculation developed by J. Welles Wilder, the initial average gain and average loss are calculated over the selected periods. Subsequent RSI values use smoothed average gains and losses as each new period is added.
Most charting platforms calculate RSI automatically, but understanding the formula helps explain what sits behind the indicator’s 0-to-100 reading.
How to calculate the Relative Strength Index
Suppose the average gain over the selected 14 periods is ₹4 and the average loss, expressed as a positive amount, is ₹2. First calculate relative strength:
RS = ₹4 / ₹2 = 2
Now use the RSI formula:
RSI = 100 − [100 / (1 + 2)]
RSI = 66.67
An RSI of 66.67 indicates that recent upward price movements have been stronger than downward movements over the selected period. However, the reading remains below the conventional overbought threshold of 70.
The figures shown are for illustrative purpose only
How does the RSI indicator work?
RSI rises when recent gains become stronger relative to recent losses and falls when recent losses become stronger. This makes it useful for reading momentum, rather than only looking at whether the price itself is moving up or down.
For example, a stock price may continue rising while RSI begins to fall, which can indicate that upward momentum is weakening even though the price has not yet reversed. Similarly, RSI may start rising while the price continues to fall, suggesting that downward momentum is losing strength.
Neither situation guarantees what the price will do next, so RSI is generally more useful when read alongside the price chart rather than in isolation.
How to interpret RSI values
The most commonly watched RSI levels are 30, 50 and 70.
| RSI level | What it generally indicates |
| 30 or below | Strong recent downward momentum and a conventional oversold condition |
| Above 30 to below 50 | Recent losses are stronger than gains, but RSI is outside the conventional oversold zone |
| Around 50 | Average gains and losses are relatively balanced |
| Above 50 to below 70 | Recent gains are stronger than losses |
| 70 or above | Strong recent upward momentum and a conventional overbought condition |
“Overbought” does not mean the price must fall next, and “oversold” does not mean it must rise. Strong trends can keep RSI at elevated or depressed levels for extended periods.
What is a bullish RSI number?
There is no single RSI number that is universally bullish. However, an RSI above 50 is commonly associated with stronger positive momentum because recent gains are outweighing recent losses. A reading of 70 or above indicates particularly strong recent upward momentum and is conventionally classified as overbought, but it does not mean the price will necessarily continue rising or reverse.
What is a bearish RSI number?
There is no single RSI number that is universally bearish. An RSI below 50 generally indicates that recent losses are stronger than gains, while a reading of 30 or below is conventionally classified as oversold. These readings indicate weaker price momentum but do not determine what the price will do next.
How RSI helps traders read momentum
RSI can help show whether a price move is strengthening, weakening or becoming unusually stretched. A rising RSI generally indicates strengthening positive momentum, while a falling RSI may reflect weakening positive momentum or strengthening negative momentum. Traders may also watch whether RSI stays consistently above or below the 50 level and whether its direction supports what is happening on the price chart.
RSI is usually more useful when read alongside actual price movement rather than focusing only on the latest number. Looking at both together can provide better context on whether momentum is building, fading or moving in line with the prevailing trend.
What is RSI divergence and what does it mean?
RSI divergence occurs when the price and RSI move in different directions. It can indicate that the momentum behind the prevailing price trend is weakening.
Bullish RSI divergence
Bullish divergence occurs when the price forms a lower low, while RSI forms a higher low. This means the price has continued falling, but the downward momentum measured by RSI has weakened.
Bearish RSI divergence
Bearish divergence occurs when the price forms a higher high, while RSI forms a lower high. Here, the price is still rising, but RSI suggests that upward momentum has weakened.
Divergence does not guarantee a price reversal. It is better treated as additional information about momentum.
NSE’s technical-analysis material also identifies RSI divergence as a technique for comparing price movement with momentum and recognises the conventional 70 and 30 reference levels.
What does RSI convergence mean?
The term RSI convergence is sometimes used to describe situations where price and RSI move broadly in the same direction. For example, rising price accompanied by rising RSI can show that price movement and momentum are aligned, while falling price alongside falling RSI can indicate that downward price movement is being accompanied by weaker momentum readings.
However, convergence is not generally treated as a distinct RSI signal in the same way as bullish or bearish divergence. It is better understood as confirmation that the indicator is broadly moving in line with the price trend.
How to interpret RSI across market trends
The same RSI value can behave differently depending on the broader market trend. Reading the indicator alongside the prevailing price structure can therefore provide more context than treating the 30 and 70 levels as fixed trading signals.
RSI during an uptrend
During a strong uptrend, RSI can remain above 50 for extended periods and may move above 70 several times. An overbought reading during such a trend does not automatically mean the uptrend is ending.
RSI during a downtrend
During a sustained downtrend, RSI may spend more time below 50 and can fall below 30 repeatedly. An oversold reading does not guarantee an immediate recovery.
RSI during a range-bound market
In a range-bound market, where prices repeatedly move between support and resistance, the conventional 30 and 70 levels may become more useful for identifying stretched momentum.
This is one reason RSI should be interpreted in the context of the market structure rather than using one set of rules for every market condition.
How to adjust RSI settings for different timeframes
The standard setting is usually 14 periods, but RSI can be calculated over shorter or longer periods. A shorter setting reacts more quickly to price changes but can also produce more frequent fluctuations and signals.
A longer setting moves more gradually and filters out some short-term price movement. The meaning of a “period” depends on the chart. A 14-period RSI on a daily chart uses daily price data, while a 14-period RSI on an hourly chart uses hourly data. There is no single RSI setting that is suitable for every trading style or market condition.
Relative strength vs Relative Strength Index (RSI)
Despite the similar names, relative strength and the Relative Strength Index are different concepts. Relative strength generally compares the performance of one security with another security or benchmark, while RSI looks at the recent gains and losses of the security being analysed and converts their relationship into a value between 0 and 100.
A stock can therefore show strong relative performance against an index while having a low RSI, or the reverse.
Advantages and limitations of RSI
RSI can be useful because it converts recent price momentum into a simple 0-to-100 scale. It can help identify unusually strong momentum, compare the balance between recent gains and losses and highlight divergence between price and momentum.
However, RSI also has limitations:
- A high or low RSI does not guarantee a reversal.
- Strong trends can remain overbought or oversold for long periods.
- RSI is based on historical price movement and does not explain why the price changed.
- Different settings and timeframes can produce different readings.
- RSI should not be treated as a standalone buy or sell signal.
Common mistakes to avoid while using RSI
A few interpretation mistakes can make RSI far less useful:
- Treating 70 as an automatic sell signal: A strong uptrend can remain above 70 for some time.
- Treating 30 as an automatic buy signal: Downward momentum can continue even after RSI enters the oversold zone.
- Confusing momentum with valuation: RSI cannot tell you whether a company is fundamentally expensive or cheap.
- Ignoring the broader trend: The same RSI level can behave differently in trending and range-bound markets.
- Using RSI alone: Price structure, volume and other market information can provide additional context.
Conclusion
The RSI indicator gives you a compact way to understand how strongly prices have been moving. Its 0-to-100 scale makes momentum easier to read, while the 30, 50 and 70 levels provide useful reference points.
The key is to treat those levels as context rather than instructions. RSI can stay unusually high or low during strong trends, and divergence may indicate weakening momentum without guaranteeing a reversal. Reading RSI alongside the price chart gives the number far more meaning.
FAQs
What is the full form of RSI?
RSI stands for Relative Strength Index, a momentum indicator used to compare recent price gains with recent price losses.
Is RSI a stock-market index?
No. Despite the word “Index” in its name, RSI is a technical indicator that measures price momentum on a scale from 0 to 100.
How is RSI used in trading?
RSI is commonly used to assess momentum, identify overbought or oversold conditions, monitor the 50 centreline and look for divergence between price and momentum.
What are the typical RSI levels for overbought and oversold conditions?
An RSI of 70 or above is conventionally considered overbought, while an RSI of 30 or below is considered oversold. These readings do not guarantee a price reversal.
Should I buy when the RSI is low?
A low RSI alone is not enough to determine whether to buy. An oversold reading shows strong recent downward momentum, but the price can continue falling.
What does RSI divergence mean in trading?
RSI divergence occurs when price and RSI move differently. A higher RSI low alongside a lower price low is bullish divergence, while a lower RSI high alongside a higher price high is bearish divergence.
What does an RSI of 70 mean?
An RSI of 70 indicates strong recent upward momentum and is commonly treated as the boundary of the overbought zone. It does not mean the price must fall.
What does an RSI of 30 mean?
An RSI of 30 indicates strong recent downward momentum and marks the conventional oversold threshold. It does not guarantee that the price will rise next.
What does an RSI of 90 mean?
An RSI of 90 indicates exceptionally strong recent upward momentum. The security is well inside the conventional overbought zone, but a high reading alone does not establish that a reversal is about to occur.
How can RSI settings be adjusted for different strategies?
Shorter RSI periods make the indicator more responsive to recent price changes, while longer periods make it smoother and less sensitive to short-term movements.
What is the difference between RSI and MACD?
RSI is a bounded momentum oscillator that moves between 0 and 100. MACD compares moving averages to assess changes in trend and momentum and does not operate within a fixed numerical range.
Is relative strength the same as RSI?
No. Relative strength compares one security’s performance with another security or benchmark, while RSI measures the balance between the security’s own recent gains and losses.
