What Is RSI
The Relative Strength Index (RSI) compares the size of recent price gains to recent price losses over a set period — typically 14 days — and converts that ratio into a single number between 0 and 100. A higher RSI reflects stronger recent buying pressure, while a lower RSI reflects stronger recent selling pressure.
As a general rule, an RSI above 70 is considered ‘overbought,’ suggesting buying momentum may be overheated and a pullback could follow, while an RSI below 30 is considered ‘oversold,’ suggesting selling pressure may be overdone and a bounce could follow.
How RSI Is Calculated
RSI is derived from the average gain divided by the sum of the average gain and average loss over the lookback period, expressed as a percentage. More up days with larger gains push RSI higher, while more down days with larger losses push it lower.
In a hypothetical five-day sequence, RSI moves from 45 to 58 to 72 to 81 and back to 68 — crossing above the overbought threshold of 70 on day four before easing back below it on day five as buying momentum cools.
Using RSI in Practice
RSI tends to work best when combined with other tools like trendlines or moving averages, rather than as a standalone signal. During strong uptrends, RSI can stay above 70 for extended periods without a meaningful pullback, so ‘overbought’ shouldn’t automatically be read as ‘sell immediately.’
A particularly notable pattern is ‘divergence’ — when a stock makes a new high but RSI fails to make a corresponding new high. This is often interpreted as a warning sign that upward momentum is weakening, even while the price itself continues rising.
| RSI Range | Interpretation |
|---|---|
| 70 and above | Overbought, possible short-term pullback |
| 50-70 | Upward momentum bias |
| 30-50 | Downward momentum bias |
| 30 and below | Oversold, possible short-term bounce |
Frequently Asked Questions
Should I sell as soon as RSI crosses above 70?
Not necessarily — during strong uptrends, RSI can remain above 70 for extended stretches without an immediate reversal, so it’s generally better to confirm the signal with other indicators before acting.
What is RSI divergence?
It occurs when the price makes a new high but RSI fails to reach a correspondingly higher level, which is often interpreted as an early warning that the uptrend’s momentum is fading.
Does changing the RSI period change the results?
Yes — the standard setting is 14 days, but shortening the period (e.g., to 9 days) makes RSI more sensitive to recent moves, while lengthening it (e.g., to 25 days) smooths the indicator out.
Does RSI work the same way for every stock?
Highly volatile stocks tend to swing between overbought and oversold zones more frequently, generating more signals, while stable large-cap stocks tend to trigger these zones less often.
Key Takeaways
RSI translates the ratio of recent gains to losses into a 0-100 scale, with readings above 70 signaling overbought conditions and below 30 signaling oversold conditions. Watching for divergence alongside the raw reading offers a more complete picture of potential trend changes. This article is for informational purposes only and does not constitute investment advice.
QuantPro: AI Finds the Trade Before You Do
From AI-powered chart analysis to real-time market intelligence — everything a serious investor needs, in one platform.
- Automated AI chart analysis with precision trend timing
- Bull Radar: real-time visualization of geopolitical & economic shifts
- Live market-moving news and insights, curated for you
Bull Wave / Bear Wave Forecast Model
Engineered to help you read market direction and momentum faster than the crowd.
- Instantly separate bullish momentum from bearish pressure
- Pinpoint high-probability entry zones with confidence
- Chart signals clear enough for beginners, sharp enough for pros
Winning Pattern Detection
Instantly surfaces the high-probability setups that repeat across the charts — a trusted edge for timing your entries and exits.
- Spot momentum building in real time
- Catch trend-reversal points before they break
- Built for active traders who need results, not theory
AI Live Economic Dashboard
AI analyzes real-time market data — turning complex, global investment flows into clear insight in seconds.
- Track global stock markets in real time
- See exactly which assets are strong — and which are fading
- Watch how geopolitical events move the markets
About the Author
