Moving Average
How a Moving Average Works
Price charts are messy. Stocks gap up, gap down, whipsaw intraday — and it’s hard to tell whether the broader trend is up, down, or sideways just by looking at raw price action. A moving average solves this by plotting a rolling average that updates with each new period.
If you apply a 50-day moving average to a chart, it takes the average closing price of the last 50 trading days and plots that as a single point. Tomorrow, it drops the oldest day and adds the newest. The result is a smooth, flowing line that tracks the trend’s direction.
Types of Moving Averages
| Type | Calculation | Best For |
|---|---|---|
| Simple Moving Average (SMA) | Equal weight to every period in the lookback window | Identifying long-term trends; widely used for the 50-day and 200-day |
| Exponential Moving Average (EMA) | More weight on recent prices, less on older ones | Faster reaction to price changes; preferred for shorter-term trading and indicators like MACD |
| Weighted Moving Average (WMA) | Linearly increasing weights from oldest to newest | Similar to EMA but with a more predictable weighting scheme |
Where P is the closing price for each period and n is the number of periods. A 20-day SMA sums the last 20 closing prices and divides by 20.
Key Moving Average Periods
| Period | Time Frame | Common Use |
|---|---|---|
| 10-day / 20-day | Short-term | Swing trading entries/exits; the 20-day is the midline of Bollinger Bands |
| 50-day | Medium-term | Most watched intermediate trend gauge; widely used support/resistance level |
| 200-day | Long-term | The institutional benchmark — price above the 200-day is broadly considered bullish |
Moving Average Signals
Golden Cross and Death Cross
The golden cross occurs when the 50-day MA crosses above the 200-day MA — a bullish signal suggesting long-term momentum is turning positive. The death cross is the opposite: the 50-day drops below the 200-day, signaling a potential long-term downtrend.
Both signals lag — by the time the crossover happens, a significant portion of the move has already occurred. They’re better as trend confirmation tools than early-warning systems.
Price Crossovers
When price crosses above a moving average, it suggests bullish momentum. When it crosses below, it suggests bearish momentum. Shorter MAs generate more signals (with more false ones). Longer MAs generate fewer signals but with higher reliability.
Moving Average as Support and Resistance
In an uptrend, stocks frequently pull back to their 50-day or 200-day MA and bounce — the moving average acts as dynamic support. In a downtrend, rallies often stall at the same moving averages, which then act as resistance.
Limitations
Moving averages are lagging indicators — they’re based on past prices, so they’ll always be a step behind current action. In choppy, range-bound markets, MAs produce frequent whipsaws where the price crisscrosses the average without establishing a real trend. They work best in strongly trending markets where direction is clear.
Key Takeaways
- A moving average smooths price data to reveal the underlying trend direction.
- The SMA gives equal weight to all periods; the EMA emphasizes recent prices for faster reaction.
- The 50-day and 200-day MAs are the most widely watched by traders and institutions.
- Golden cross (50 above 200) is bullish; death cross (50 below 200) is bearish — but both lag.
- MAs act as dynamic support in uptrends and resistance in downtrends.
Frequently Asked Questions
Which is better, SMA or EMA?
Neither is objectively better. EMAs react faster to recent price changes, making them popular for short-term trading and indicators like MACD. SMAs are smoother and less prone to whipsaws, making them the standard for longer-term trend analysis. Many traders use both — an EMA for entries and an SMA for trend confirmation.
What’s the best moving average period to use?
It depends on your time frame. Day traders often use 9- or 21-period EMAs. Swing traders favor the 20- or 50-day. Long-term investors watch the 200-day. There’s no universal “best” — the right period matches your holding horizon.
Do moving averages predict the future?
No. Moving averages are lagging indicators built entirely from past prices. They confirm trend direction and provide reference levels for support/resistance, but they don’t forecast where price is going — they show where it’s been.