What is EMA?
In short
Exponential moving average: weights recent prices more heavily, so it reacts faster than an SMA.
Also known as: exponential moving average
The EMA (exponential moving average) is an average that gives more weight to recent prices. In a plain SMA each of the last 20 days counts equally; in an EMA today's price counts more than yesterday's, and yesterday's more than the day before. As a result the EMA reacts to price changes faster.
Formula
- Multiplier: k = 2 ÷ (N + 1).
- EMA today = (Close − EMA yesterday) × k + EMA yesterday.
The first value is usually seeded with the SMA of the same period. For a 9-period EMA, k = 2 ÷ 10 = 0.2, meaning today's price enters the average with a 20% weight.
Popular settings
- 9 and 21 EMA — short-term trading, intraday and swing.
- 12 and 26 EMA — the basis of the MACD indicator.
- 50 and 200 EMA — some traders use them instead of the SMA.
When it is useful
On fast-moving stocks and lower timeframes, the EMA shows trend changes earlier than the SMA. In strong trends price often pulls back to the 9 or 21 EMA and bounces.
Limitations
The price of speed is sensitivity to noise. The EMA reacts quickly to random swings too, so in sideways markets it gives even more false signals than the SMA. It is still built from past prices and still lags — just less.
MACD = EMA 12 (blue) − EMA 26 (amber). First MACD crossed above its signal line (price $84.20) — the earliest but least reliable hint. Later EMA 12 crossed above EMA 26 ($86.55 > $86.44), i.e. MACD turned positive (price $89). Stronger confirmation, but later.
Example
Illustrative case, a 9-period EMA (k = 0.2). Yesterday's EMA was $50.00 and today the stock closes at $55.00.
- EMA today = ($55 − $50) × 0.2 + $50 = $1 + $50 = $51.00.
For comparison, a 9-day SMA, assuming the previous 8 days all closed at $50 and today at $55:
- SMA = (8 × $50 + $55) ÷ 9 = $455 ÷ 9 ≈ $50.56.
On the same price jump the EMA rose $1.00 while the SMA rose only about $0.56. The EMA reflected the new move almost twice as strongly.
Mistakes and tips
Short EMAs (9, 21) are noisy — use them as dynamic levels only in strong trends.
Don't treat EMA crossovers as trade signals without confirmation: in ranges they produce strings of losses.
Don't load a chart with many averages — two or three is plenty; more just adds confusion.
Frequently asked questions
- What is the difference between EMA and SMA?
- The SMA weights all prices equally, the EMA weights recent prices more. So the EMA shows turns sooner but also gives more false signals.
- Which EMA is used for day trading?
- Many traders use the 9- and 21-period EMAs, but there is no universally correct setting — what matters is using your chosen setting consistently.
Learn it in the Academy
This term is covered with hands-on examples and a quiz in these lessons of the interactive course.
- Trend: swimming with the currentHH/HL structure, trendlines and channels, the 20/50/200-day averages, buying pullbacks and the signs that a trend is ending.Open lesson · 11 min
- Volume and core indicatorsVolume and relative volume, RSI in trends and ranges, MACD, VWAP and moving averages — when each one helps and when it misleads.Open lesson · 11 min
- Stop-loss: admitting you're wrong in timeWhere to put the stop (structure and ATR), which types exist, gaps and slippage, trailing methods, the pros and cons of moving to breakeven, and the costliest mistakes.Open lesson · 11 min
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