What it is made of
Take a fast moving average and subtract a slow one; the result is the MACD line. The usual settings are a twelve-period and a twenty-six-period exponential average, with a nine-period average of the MACD line drawn on top as the signal line. The histogram is the gap between those two. Nothing in there is new information — it is three arrangements of the same past prices.
The zero line
The MACD line is above zero when the fast average is above the slow one, and below zero when it is not. So the zero line is a trend statement in one glance: above it the recent past is stronger than the longer past. Crossings of zero are slower and less frequent than crossings of the signal line, which makes them less noisy and even later.
Crossovers
When the MACD line crosses above its signal line, the gap between the two averages is widening upward — momentum is picking up. That is the standard buy reading and it is late by construction, because an average of an average cannot turn before the price does. In a trend it works; in a range it produces a cross every few candles, most of them worthless.
The histogram, read properly
The bars shrink when the two lines converge and grow when they separate. Shrinking bars during a rally mean the push is losing force — that is the earliest thing MACD says, and it is a warning rather than a signal. A shrinking histogram is not a reason to sell; it is a reason to stop adding, tighten a target, or wait for the level to do the deciding.
Divergence
Price makes a higher high and the MACD does not: the second push was weaker than the first. That is a true observation about momentum and it is not a timing tool — divergence can persist through a trend for a long time. It is worth something at a level and worth nothing in open space, which is the same sentence that applies to RSI divergence.
Honest limits
Every value on the chart is derived from prices that have already happened, so MACD cannot lead. It whipsaws in ranges, its settings are conventions rather than discoveries, and changing them to fit a past chart is how a curve gets fitted. It is a description of momentum, useful for filtering, and it is not a system.
In short
| MACD line | Fast average minus slow average |
|---|---|
| Usual settings | 12 and 26, with a 9-period signal |
| Signal line | An average of the MACD line |
| Histogram | The gap between the two lines |
| Above zero | The fast average is above the slow one |
| Honest limit | Derived from past price, so always late |
Common questions
What do the numbers 12, 26 and 9 mean?
Periods for the fast average, the slow average and the signal line. They are a convention, not a discovery, and tuning them to fit an old chart is curve fitting.
Is a MACD cross a buy signal?
It is a statement that momentum has picked up, and it arrives after the move has started. Used as a filter on a trade you already had a reason for, it helps; used alone in a range, it produces losses in both directions.
MACD and RSI — do I need both?
They measure related things in different ways, and stacking indicators that agree with each other feels like confirmation without being any. One momentum tool is usually enough.
Trading forex and CFDs on margin carries a high level of risk. Most retail accounts lose money. Nothing on this page is financial advice or a recommendation to trade.