MACD Line, Signal Line, and Histogram: What Each Shows
Distinguish the three MACD components, zero-line crossovers, and signal-line crossovers. Learn why price can rise while the histogram shrinks and why raw MACD values are hard to compare across stocks.
The MACD line is the difference between moving averages of different periods, and the signal line is an average of that difference. The histogram equals the MACD line minus the signal line. Zero-line and signal-line crossovers compare different things and should not be treated as the same signal.
Start with how the three components are calculated
A widely used setting subtracts the 26-period EMA from the 12-period EMA to create MACD, then uses a 9-period EMA of that value as the signal line. These are conventional settings, not an optimal answer for every stock. A positive MACD means the short-term average is above the long-term average; a positive histogram means MACD is above its own signal line. Distinguishing the two lets you describe conditions such as a short-term recovery below the long-term average. If a platform allows different averaging methods, identical period numbers do not necessarily mean identical calculations.
Shorter histogram bars do not necessarily mean a falling share price
A shrinking positive histogram means the gap between MACD and its signal line is narrowing. The gap can shrink even while MACD rises gradually, as the signal line catches up. In other words, bars can get shorter while the share price continues rising if the pattern of its upward momentum changes. Conversely, shrinking negative bars can suggest easing weakness but do not confirm an upward price reversal. Depending on the service, bar colors may represent the sign or the change from the previous bar, so check the color legend as well.
How to compare an indicator without a fixed range
Unlike RSI, MACD is not confined to a range of 0 to 100; it is affected by price level and the size of price changes. Comparing only the MACD readings of two stocks with very different share prices to decide which company is stronger mixes in differences in scale. Compare the same stock over time with consistent settings, or check the definition of a separate indicator that converts the values to a relative measure. Signal-line crossovers can become frequent in sideways periods. Include subsequent price movement and costs alongside crossover counts to assess whether the indicator actually adds information that helps distinguish conditions.
Worked example
Hypothetical example: If the short-term EMA is 105 won and the long-term EMA is 100 won, MACD is 5 won. If the signal line is 4 won, the histogram is 1 won. If MACD on the next bar is 5.2 won, applying the 9-period EMA weight of 0.2 gives a signal of 5.2×0.2+4×0.8=4.24 won, and the histogram shrinks to 5.2−4.24=0.96 won. MACD rose, but the histogram bar became smaller. This calculation cannot be translated into “the share price fell”; check the actual close and changes in both averages again.
What to check
- Check the short, long, and signal periods and the averaging methods.
- Distinguish the sign of MACD from the sign of the histogram.
- Check whether bar colors show the sign or the change in value.
- Do not directly compare raw MACD magnitudes across stocks.
Sources and primary materials
This is educational material about research methods. For an actual company decision, verify the filings and primary sources for the relevant period.