Indicator: What Is RSI? Finding Overbought/Oversold Zones

RSI (Relative Strength Index) is an oscillator-type indicator used to measure the strength and speed of price changes. It ranges from 0-100 and is commonly used to spot moments where price may be "overbought" or "oversold."

How RSI Is Calculated (the Intuition)

RSI compares the size of recent up-moves against recent down-moves over a lookback period — 14 candles by default. If every one of the last 14 candles closed higher, RSI approaches 100; if every one closed lower, it approaches 0; if gains and losses were balanced, it sits near 50. You never need to compute it by hand, but knowing this explains its behavior: RSI is high because recent candles were mostly bullish, nothing more mystical than that.

The period setting tunes its sensitivity: a shorter RSI (e.g. 7) swings to extremes often and reacts fast; a longer one (e.g. 21) is smoother and reaches overbought/oversold only on truly stretched moves. The default 14 is the standard most traders share.

How to Read RSI

• RSI above 70 — interpreted as the Overbought zone, price may have a chance of pulling back or reversing down.
• RSI below 30 — interpreted as the Oversold zone, price may have a chance of bouncing back or reversing up.
• RSI around 50 — indicates buying and selling pressure are roughly equal, with no clear direction yet.

A subtle but important detail: the meaningful signal is usually not RSI entering the extreme zone, but RSI leaving it — crossing back below 70 or back above 30. Entering overbought just means momentum is strong; the exit is the first evidence that momentum is actually turning.

The 50 line has a second life as a trend filter: in healthy uptrends, RSI tends to oscillate roughly between 40 and 80, holding above ~40-50 on pullbacks; in downtrends, between 20 and 60. Where RSI spends its time tells you which regime you're in — useful context from Trend vs Range.

A Word of Caution

In a strongly trending market, RSI can stay in the Overbought or Oversold zone for a long time while price keeps moving in the same direction — a strong uptrend is, by definition, a market that keeps closing higher, which is exactly what pins RSI above 70. Using RSI alone to trade against the trend carries high risk, so always consider the main price trend alongside it. RSI's overbought/oversold readings are most trustworthy in ranging markets, where price genuinely does rotate between extremes.

Bullish / Bearish Divergence

Divergence happens when the direction of price and the direction of RSI move opposite to each other. For example, price makes a new low that is lower than the previous one, but RSI makes a low that is higher than its previous low (Bullish Divergence), which can be an early warning sign that selling pressure is starting to weaken. The mirror case — price making a higher high while RSI makes a lower high (Bearish Divergence) — warns that an uptrend's momentum is fading even as price grinds to new highs.

Two things keep divergence honest:

1. It's a warning, not an entry. Divergence says momentum is fading, not that price will reverse now — divergences can stack two or three times in a strong trend before anything happens. Wait for confirmation: a candlestick reversal pattern, a break of structure, or RSI exiting its extreme zone.
2. Compare swing to swing. Valid divergence is measured between clear swing lows (or highs) on both price and RSI — not between arbitrary wiggles picked to fit the story.

How Traders Combine RSI with Other Tools

RSI answers "is this move stretched?" — it pairs naturally with tools that answer "where" and "which direction":

• RSI + support/resistance — an oversold reading at a tested support level is a far stronger setup than an oversold reading in the middle of nowhere.
• RSI + trend filter — a common discipline: in an uptrend (price above a 50-period Moving Average), only take oversold/buy signals and ignore overbought ones; reverse in a downtrend. This turns RSI from a counter-trend trap into a pullback-entry timer.
• RSI + Stochastic — similar oscillators; comparing them is mostly useful for learning, not for stacking as "double confirmation," since they largely repeat each other.

Download the Indicator

This custom indicator calculates RSI and automatically alerts when price enters the Overbought or Oversold zone based on your settings. It's available for both MetaTrader 4 and MetaTrader 5 below.

How to Install — MetaTrader 4

1. Download the rsi-alert.mq4 file below.
2. Open MetaTrader 4 → click File → Open Data Folder.
3. Place the file in the MQL4/Indicators folder.
4. Restart MetaTrader 4, then drag the indicator from the Navigator window onto the chart.

How to Install — MetaTrader 5

1. Download the rsi-alert.mq5 file below.
2. Open MetaTrader 5 → click File → Open Data Folder.
3. Place the file in the MQL5/Indicators folder.
4. Restart MetaTrader 5, then drag the indicator from the Navigator window onto the chart.

Both files are source code — open and review the full code before using it, for your own safety.