Recently, I’ve been chatting with novice investors and found that many people have a love-hate relationship with the bunch of technical indicators in stock trading software. The dense array of tools can be overwhelming to look at, but they also want to learn how to use them. Today, I want to talk about one I use most frequently—the KD indicator.

Honestly, when used correctly, the KD indicator can help you catch many entry and exit points, but you also need to understand its temperament.

First of all, the full name of the KD indicator is the Stochastic Oscillator, introduced by American George Lane in the 1950s. The core logic of this indicator is simple: look at the high and low price changes over a period, then judge whether the current price is strong or weak within that range. The KD indicator’s values range from 0 to 100, consisting of two lines: K (fast line) and D (slow line). The K line reacts more sensitively, while the D line is a smoothed version of K, usually set as a 3-period simple moving average of K.

In practical operation, the most basic thing is to observe the position of these two lines. When the K line crosses above the D line, it’s called a golden cross, which is usually a buy signal; when the K line drops below the D line, it’s called a death cross, and you might consider selling.

Regarding how to use the KD indicator, the most straightforward method is to look at the value levels. When the KD value exceeds 80, it indicates the stock is performing strongly, but be cautious because it might have risen too rapidly in the short term, with a roughly 95% chance of a subsequent decline and only a 5% chance of further rise. Conversely, when the KD value is below 20, it indicates the stock is weak, oversold in the short term, and likely to rebound, with about a 95% probability of bouncing back. If the KD value hovers around 50, it suggests a balance of bullish and bearish forces, and you can choose to wait or trade within a range.

But here’s a very important point—overbought doesn’t mean it will immediately fall, and oversold doesn’t mean it will instantly rise. These values are only risk warning signals, not infallible indicators.

When I use the KD indicator myself, I also encounter some issues. For example, sometimes the indicator hovers at high or low levels for a prolonged period, which is called a stagnation phenomenon. High-level stagnation means the stock price keeps rising, but the KD indicator stays in the 80-100 range for a long time. At this point, you don’t know whether to sell or hold. My experience is that in such situations, you must combine other indicators and fundamental news to make a judgment. If there are positive signals, you can observe further; if there are negative signals, you should quickly adjust your strategy and exit in stages.

Another phenomenon is divergence, where the stock price movement and the KD indicator trend do not match. For example, if the stock hits a new high but the KD does not, it’s called positive divergence, which is usually a sell signal. Conversely, if the stock hits a new low but the KD does not, it’s called negative divergence, often a buy signal. However, divergence is not 100% accurate, so it must be used together with other indicators for confirmation.

The KD parameter is usually set to 14 days, but this can be adjusted according to your trading style. For short-term trading, you might use a 5- or 9-day cycle for more sensitivity; for long-term investing, 20 or 30 days can make the indicator smoother.

Having said all these benefits, I also need to be honest about the drawbacks of the KD indicator. First, if the parameters are set too small, the response becomes overly sensitive, generating too much noise, making it hard to trust the signals. Second, stagnation can cause you to miss large market moves. Additionally, signals can be too frequent at times, requiring the use of multiple cycles and other indicators for confirmation. Lastly, the KD indicator is ultimately a lagging indicator—it’s based on historical data, so don’t over-hype it.

Therefore, my advice is to treat the KD indicator as a risk warning tool, not a magic panacea. It should be combined with other technical indicators and fundamental analysis to truly reduce risk and improve your winning chances. If you’re into short-term trading, besides technical signals, make sure to set proper stop-loss and take-profit points—that’s the right way to invest.