MACD: trend and momentum in one

MACD, short for Moving Average Convergence Divergence, is one of the most popular indicators because it says something about both the direction of a trend and its momentum. It is built from the difference between two exponential moving averages, so like them, it lags price.

The parts of MACD

The common default settings are 12, 26 and 9. They produce three components:

1. MACD line: the 12-period EMA minus the 26-period EMA.
2. Signal line: a 9-period EMA of the MACD line itself.
3. Histogram: the distance between the MACD line and the signal line, drawn as bars.

When the MACD line is above zero, the shorter average is above the longer one and the broad backdrop is bullish. Below zero suggests the opposite.

Common ways to read MACD

Signal line crossovers

A cross of the MACD line above the signal line is usually read as rising bullish momentum, and a cross below as rising bearish momentum. In trendless markets these crosses are frequent and carry little value.

Zero line crosses

A zero line cross is effectively the two EMAs crossing each other. It is a slower signal of trend change but often a more durable one.

Histogram and divergence

Shrinking histogram bars show that momentum is fading, even while price is still moving in the same direction. Growing bars, by contrast, mean the gap between the two lines is widening and the move is accelerating. Some traders therefore watch the histogram turn before the lines actually cross, accepting that this extra sensitivity also brings more false signals. As with RSI, divergence between price highs or lows and MACD can give an early warning that a trend is weakening.

Limitations

MACD has no fixed scale such as 0 to 100; its values depend on the price of the asset. That means there is no universal "overbought" level, and you cannot compare MACD readings between different instruments, for example Bitcoin and EUR/USD. Tweaking the default settings until past results look better also carries a real risk of over-fitting.

Key takeaways

• MACD is built from the difference between two EMAs and lags price.
• Above zero points to a bullish backdrop, below zero to a bearish one.
• The histogram shows changes in momentum earlier than crossovers do.
• MACD values cannot be compared across different assets.