What is MACD?
The Moving Average Convergence Divergence indicator, created by Gerald Appel in the late 1970s, consists of three components: the MACD line (12-period EMA minus 26-period EMA), the signal line (9-period EMA of the MACD line), and the histogram (difference between the MACD and signal lines). When the MACD line crosses above the signal line, it generates a bullish signal; a cross below generates a bearish signal. The histogram visually represents the momentum behind these crossovers.
Reading MACD Signals
The most reliable MACD signals occur when crossovers align with the zero line. A bullish crossover above zero confirms an established uptrend, while a bearish crossover below zero confirms a downtrend. Divergences between MACD and price action are particularly valuable: if a stock makes a new high but the MACD histogram is declining, it warns of fading momentum. Histogram peaks and troughs often precede actual MACD line crossovers by 1 to 3 bars, giving attentive traders an early warning.
Key Considerations
MACD is a lagging indicator because it is derived from moving averages, so it will always be late to signal trend changes. In choppy, sideways markets, MACD generates frequent false crossovers known as whipsaws. Traders can reduce false signals by requiring the MACD histogram to exceed a minimum threshold before acting, or by combining MACD with a trend filter such as the 200-day moving average. The default 12/26/9 parameters work well for daily charts but should be adjusted for shorter or longer timeframes.