Simple Moving Average (SMA) Explained
The oldest indicator in existence. Still one of the most useful.
Researched and written by Laurent The Calculation
A Simple Moving Average (SMA) adds the closing prices of the last N candles and divides by N. Each new candle, the oldest price drops off and the newest is added. The result is a smooth line that follows price at a delay.
Closing prices: 1.0810, 1.0825, 1.0840, 1.0830, 1.0855
SMA(5) = (1.0810 + 1.0825 + 1.0840 + 1.0830 + 1.0855) / 5 = 1.0832
The Popular Periods and What They Mean
Traders tend to cluster around the same SMA periods because self-fulfilling prophecy is real: when millions of traders watch the same level, price genuinely reacts there.
| SMA Period | Represents | Typical Use |
|---|---|---|
| 20 SMA | ~1 month of trading days | Short-term trend, mean reversion targets |
| 50 SMA | ~2.5 months | Medium-term trend direction, swing support/resistance |
| 100 SMA | ~5 months | Medium-long term trend, less common than 50/200 |
| 200 SMA | ~10 months (1 year on daily) | The definitive long-term trend indicator, watched by institutions |
The 200 SMA: The Most Important Line on Your Chart
The 200-period SMA on the daily chart is the single most-watched technical level in professional trading. Fund managers, banks, and institutional algorithms all reference it. Here's what it tells you:
- Price above 200 SMA: The long-term trend is up. Prefer buy setups. Be cautious on shorts.
- Price below 200 SMA: The long-term trend is down. Prefer sell setups. Be cautious on longs.
- Price crossing the 200 SMA: A significant shift in trend is occurring. Major attention from all market participants.
SMA as Dynamic Support and Resistance
In a trending market, price frequently "bounces" off moving averages. In an uptrend, the 50 SMA often catches pullbacks. This happens because many traders set buy orders near the SMA anticipating this bounce, which then makes the bounce happen.
The key word is "dynamic": unlike horizontal S/R levels, the SMA moves with price. A support level at the 50 SMA today might be 50 pips lower next week if price keeps rising.
Limitations of the SMA
The SMA gives equal weight to all prices in its window. The price from 200 days ago counts as much as yesterday's price. In fast-moving markets, this makes the SMA slow to react. That's why many traders prefer the EMA, which we'll cover in the next lesson.
Also: in ranging markets, the SMA lines become flat and price crosses them repeatedly in both directions, generating many false signals. SMAs work best in trending conditions. Learning to identify when a market is trending versus ranging is as important as knowing the indicator itself.
Key Takeaways
- • SMA = average of the last N closing prices, recalculated with each new candle.
- • Common periods: 20 (short-term), 50 (medium-term), 200 (long-term).
- • Price above 200 SMA = generally bullish environment. Below = generally bearish.
- • SMAs act as dynamic support and resistance: price often reacts when it touches them.