What Is the RSI (Relative Strength Index)?
The Relative Strength Index (RSI) is a momentum oscillator that measures the speed and magnitude of a stock's recent price changes, expressed on a scale from 0 to 100. A reading above 70 signals a potentially overbought stock; below 30, a potentially oversold one.
Developed by J. Welles Wilder Jr. in 1978, RSI is one of the most widely used technical indicators in equity markets. Unlike price alone, RSI tells you not just where a stock's price is, but how fast it got there — and whether that speed is becoming extreme.
TL;DR: RSI is a 0–100 momentum gauge. Above 70 = overbought (the stock may have run too far, too fast). Below 30 = oversold (the stock may be due for a bounce). The standard look-back period is 14 days. You can filter stocks by RSI in ScreenerHub to instantly surface setups worth investigating.
Why RSI Matters for Stock Screening
Most stock metrics measure what a company is worth — earnings, revenue, book value. RSI measures what the market is doing with a stock's price right now. That distinction matters because valuation alone rarely tells you when to act.
Consider two stocks, both trading at fair value according to their P/E ratio. One has been climbing steadily for six weeks; its RSI is 74 and rising. The other just dropped 15% in three sessions on no fundamental news; its RSI is 26. The underlying businesses might be identical — but the near-term setups are completely different.
RSI adds a timing layer to fundamental screening. It doesn't replace quality filters like earnings growth or market cap, but it tells you whether a stock is in an extreme momentum state right now — which can be exactly the kind of edge a systematic screener is built to find.
What RSI adds to a fundamental screen
| Without RSI | With RSI |
|---|---|
| Good stock, but entered at a recent peak | Filter to stocks that are also oversold (< 30) |
| No context on current price momentum | Momentum context visible at a glance |
| Misses short-term mean-reversion setups | Surfaces potential bounce candidates |
| Misses overbought risk in trend-following | Flags stocks that may have run ahead of value |
How RSI Is Calculated
RSI is calculated over a rolling window — the default is 14 periods (14 trading days for daily charts). The formula compares average gains to average losses over that window.
Where:
- Average Gain = average of all up-day closes over the period
- Average Loss = average of all down-day closes over the period (as a positive number)
- RS = the ratio of average gain to average loss
When gains dominate, RS is large, and RSI approaches 100. When losses dominate, RS approaches 0, and RSI approaches 0.
A concrete example
Suppose a stock closes higher on 10 of the last 14 days, with an average gain of $1.20 on up days and an average loss of $0.40 on down days.
An RSI of 75 puts this stock firmly in overbought territory.
| Avg Gain | Avg Loss | RS | RSI | Zone |
|---|---|---|---|---|
| $1.20 | $0.40 | 3.0 | 75.0 | Overbought |
| $0.80 | $0.80 | 1.0 | 50.0 | Neutral |
| $0.30 | $0.90 | 0.33 | 25.0 | Oversold |
| $0.10 | $1.50 | 0.07 | 6.3 | Deeply oversold |
These are not guarantees — RSI describes momentum, not direction. A stock with RSI of 75 can keep climbing.
How to Interpret RSI Values
RSI zones and what they signal
| RSI Range | Label | What It Typically Signals |
|---|---|---|
| > 70 | Overbought | Strong recent buying pressure; stock may be extended and due for a pullback |
| 50–70 | Bullish momentum | Price is trending upward; buyers are in control |
| 50 | Neutral | Roughly equal buying and selling pressure over the period |
| 30–50 | Bearish momentum | Price is trending downward; sellers are in control |
| < 30 | Oversold | Strong recent selling pressure; stock may be due for a bounce |
⚠️ Context matters: In a strong uptrend, RSI can stay above 70 for weeks. In a strong downtrend, it can remain below 30. The overbought/oversold labels are starting points for investigation — not automatic buy or sell signals.
RSI divergence — when the signal goes deeper
One of the most powerful applications of RSI isn't the absolute level, but how it moves relative to price:
- Bullish divergence: Price makes a new low, but RSI makes a higher low. Selling momentum is weakening even though price is still falling — often a leading indicator of a reversal.
- Bearish divergence: Price makes a new high, but RSI makes a lower high. Buying momentum is fading even though price is still rising — often a leading indicator of a top.
Divergences are harder to screen for automatically, but they're one reason traders watch RSI closely alongside price charts.
RSI in a Stock Screener
RSI becomes especially powerful when combined with fundamental quality filters. The logic: find stocks that are genuinely good businesses and currently in an oversold or momentum state.
Screener 1: Oversold quality stocks (mean reversion)
Find high-quality companies that have been temporarily sold off — potential bounce candidates.
| Filter | Setting |
|---|---|
| RSI (14-day) | < 30 |
| Market cap | > $1B |
| P/E ratio | 5 – 25 |
| Debt-to-equity | < 1.5 |
This screen surfaces companies with real earnings that the market has aggressively sold — often after sector rotation, earnings disappointments, or macro-driven selloffs. Not every result will bounce, but you've narrowed the universe to situations worth investigating.
→ Try this screen in ScreenerHub: RSI < 30 →
Screener 2: Momentum breakout watch
Find stocks with strong upward momentum — for trend-following strategies.
| Filter | Setting |
|---|---|
| RSI (14-day) | 55 – 70 |
| Market cap | > $500M |
| Revenue growth | > 10% |
An RSI in the 55–70 range shows strong momentum without being in extreme overbought territory. Combined with revenue growth, this targets companies with fundamental momentum backing up the price momentum.
Screener 3: Deeply oversold small caps
High-risk, high-reward setups in small-cap names.
| Filter | Setting |
|---|---|
| RSI (14-day) | < 25 |
| Market cap | $100M–$2B |
| Volume | > average |
Common Mistakes When Using RSI
1. Treating overbought/oversold as automatic signals A stock with RSI above 70 can continue rising for months in a strong bull market. RSI above 70 is a reason to look more closely — not a reason to short. Always check the fundamental context and the broader trend before acting.
2. Using RSI in isolation RSI measures momentum, not value or quality. A stock can be both oversold (RSI = 25) and a genuinely poor business heading lower. Pair RSI with earnings, market cap, and debt metrics to filter out fundamental dead-weight from the results.
3. Using the wrong time period for your strategy The default 14-day RSI measures short-term momentum. Swing traders might shorten it to 9 days for more sensitivity. Long-term investors might use weekly RSI to filter out daily noise. Match the RSI period to your holding horizon.
Frequently Asked Questions
What does RSI above 70 mean?
An RSI above 70 means the stock has experienced stronger buying pressure than selling pressure over the lookback period (typically 14 days). It signals that the stock may be overbought — i.e., price has risen quickly and might be due for a pullback. However, in strong uptrends, stocks can stay overbought for extended periods.
What is a good RSI level to buy a stock?
Most traders watch for RSI dropping below 30 as a potential entry signal — the stock may be oversold and due for a bounce. However, RSI alone is not a sufficient buy signal. The best setups combine an oversold RSI reading with solid fundamentals (earnings, manageable debt, positive free cash flow) and a clear catalyst or support level.
How is RSI different from MACD?
Both are momentum indicators, but they measure different things. RSI measures the relative magnitude of recent gains versus losses on a fixed 0–100 scale. MACD (Moving Average Convergence Divergence) measures the difference between two moving averages and is more useful for identifying trend changes and momentum shifts. Many traders use both together: RSI for overbought/oversold levels, MACD for trend direction confirmation.
What time period does ScreenerHub use for RSI?
ScreenerHub calculates RSI using the standard 14-day period on daily closing prices — the industry default established by Wilder and used by Bloomberg, TradingView, and most professional platforms. You can use the RSI filter in the Screener Studio to set custom thresholds for overbought, oversold, or any momentum range.