Moving Average Convergence Divergence
To calculate the MACD subtract the 26-day exponential moving average (EMA) from a 12-day EMA. A 9-day dotted EMA of the MACD called the signal line is then plotted on top of the MACD. Other lengths of average can be used, but 9-12-26 is the most common "standard" setting.
MACD measures the difference between two moving averages. A positive MACD indicates that the 12-day EMA is trading above the 26-day EMA. A negative MACD indicates that the 12-day EMA is trading below the 26-day EMA. If MACD is positive and rising, then the gap between the 12-day EMA and the 26-day EMA is widening. This indicates that the rate-of-change of the faster moving average is higher than the rate-of-change for the slower moving average. Positive momentum is increasing and this would be considered bullish. If MACD is negative and declining further, then the negative gap between the faster moving average and the slower moving average is expanding. Downward momentum is accelerating and this would be considered bearish.
There are 3 common methods to interpret the MACD1: