Just recently, someone asked me what RSI is, so I might as well organize the core points of this indicator.

Honestly, if you're just starting to get into technical analysis, the Relative Strength Index (RSI) is definitely a must-learn. This tool is simple to use but quite powerful; many traders rely on it as a reference for judging buy and sell timing.

The logic behind RSI is quite straightforward: it compares the magnitude of recent upward and downward price movements over a certain period to see which side is stronger. The calculation isn't complicated either—select a period (usually 14 days), sum up the gains and losses separately and average them, then divide the average gain by the average loss, and plug into the formula RSI = 100 - (100 ÷ (1 + RS)) to get a value between 0 and 100.

How to interpret this value? An RSI above 70 indicates overbought conditions, meaning the price has risen too much and may pull back; below 30 indicates oversold conditions, suggesting the price has fallen too hard and may rebound. But there's a pitfall: in strong trending markets, RSI can become overextended and stay in extreme zones for a long time, causing overbought/oversold signals to become invalid. In such cases, it's necessary to combine RSI with other indicators for better judgment.

One of my favorite signals is RSI divergence. Divergence occurs when the price and RSI move in opposite directions. For example, if the price hits a new high but RSI doesn't follow and instead declines, that's called bearish divergence, often indicating weakening upward momentum and a possible correction. Conversely, if the price hits a new low but RSI doesn't make a new low and starts to rebound, that's bullish divergence, which often signals a potential trend reversal from down to up. However, divergence isn't foolproof—especially in strong trends, divergence can persist for a long time before a reversal occurs, so patience and confirmation are needed.

Another practical approach is to look at RSI in relation to the 50 midline. An RSI above 50 suggests bullish strength, indicating a potentially optimistic outlook; below 50 suggests bearish strength, indicating a possible downtrend. This midline can serve as a dividing line between bullish and bearish conditions.

For more precise analysis, traders often set multiple RSI lines with different periods, such as 6, 12, and 24 days. If these multiple lines form a W pattern below 50, it indicates weakening bearish momentum and a possible rebound; if they form an M pattern above 50, it suggests weakening bullish momentum and a potential decline. When a short-term RSI crosses above a long-term RSI, it's called a golden cross—often a good entry point; the opposite, a death cross, may signal it's time to close positions.

Parameter settings are also important. The standard 14-day RSI suits most situations, but you can adjust based on your trading style. For short-term trading, shortening the period to 5 or 7 days makes RSI more sensitive; for medium to long-term trading, extending it to 20 or 30 days helps filter out short-term noise.

Finally, a reminder: although RSI is a useful tool, it’s only a reference—not an absolute predictor. Overextensions and divergence failures can happen, so it’s crucial to combine RSI with other indicators like moving averages, MACD, volume, etc., for comprehensive analysis. Also, always set strict stop-losses to survive longer in the market.