EMA vs SMA: The Exponential Moving Average
Like the SMA, but smarter about recent price action.
Researched and written by Laurent Why EMA Exists
The SMA's weakness is its equal weighting. If EUR/USD makes a big move on day 1 and then ranges quietly for 199 days, the SMA still gives that day-1 move equal importance on day 200. The EMA fixes this by assigning exponentially decreasing weight to older prices.
The result: the EMA reacts faster when price makes a significant move, and it "forgets" old data more quickly.
The Multiplier
Each period has a smoothing multiplier. For a 10-period EMA, the multiplier is 2 / (10 + 1) = 0.1818. This means today's closing price gets roughly 18% weight in the calculation, while yesterday's EMA value carries the rest. The further back a candle is, the smaller its contribution.
EMA today = (Close today × Multiplier) + (EMA yesterday × (1 − Multiplier))
For a 9-period EMA: Multiplier = 2/(9+1) = 0.20
So: today's EMA = (Today's close × 0.20) + (Yesterday's EMA × 0.80)
Popular EMA Periods
| EMA Period | Used For | Traders Who Use It |
|---|---|---|
| 9 EMA | Very short-term momentum | Day traders, scalpers |
| 21 EMA | Short-term trend, fast swing | Swing traders, forex day traders |
| 50 EMA | Medium-term trend | Swing to position traders |
| 200 EMA | Long-term trend (same role as 200 SMA) | All timeframes |
EMA vs SMA: The Practical Difference
The EMA stays closer to price during trending moves. In the early stages of a trend, the EMA will show the trend sooner than the SMA. In the later stages of a trend, the EMA will also reverse sooner, which can mean more false signals during choppy periods.
There is no universally "better" choice. The practical rule most experienced traders use:
- Use SMA 200 as the master trend filter (long-term, slow, stable).
- Use EMA 21 or EMA 50 for trade management (dynamic S/R for active trades).
- Use EMA 9 as a short-term momentum indicator on intraday charts.
The "EMA Ribbon"
Some traders plot multiple EMAs simultaneously (e.g., 9, 21, 50) to get a visual sense of trend structure. When the fast EMA is above the medium EMA, which is above the slow EMA, and all are pointing up, it signals a strong uptrend. When they're tangled and flat, it signals a range.
Key Takeaways
- • EMA gives more weight to recent prices, making it faster to react than SMA.
- • Popular EMAs: 9, 21, 50, 200.
- • EMA is preferred for short-term trading; SMA is better for long-term trend analysis.
- • In practice: use EMA for entries and exits, SMA for the overall trend filter.