What Is EMA in Stock Trading? How Does It Work?

By Laurel Tincher · March 08, 2022 · 5 minute read

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What Is EMA in Stock Trading? How Does It Work?

An exponential moving average (EMA) is a commonly used average price calculation done for a specific time period that places more weight and importance on the most recent price data. Since it is weighted this way it reacts faster to recent price changes than a simple moving average (SMA) which is a type of average price calculation, which equally weights all data points within a time period.

Moving averages are technical analysis trading indicators used by traders to help them understand the direction, market trend, and strength of price movement of an asset. They measure the average price of a security by taking averages of the prices of the security over a specific period of time, and can be used to show traders the location of support and resistance levels. Read on to learn more about the meaning of EMA in stocks, the EMA formula, and how to calculate EMA.

What is an Exponential Moving Average (EMA)?

An EMA, exponentially weighted moving average, is a type of moving average (MA) used by traders to evaluate the potential trajectory of a financial security. Using the EMA calculation, the most recent price data has the greatest impact on the moving average, while older data has a lower impact. The previous EMA value is included in the calculation, so the current value includes all the price data.

EMA Formula

The formula for calculating EMA is:

EMA = (K x (C – P)) + P


C = Current Price

P = Previous Period’s EMA (for the first period calculated the SMA is used)

K = Exponential Smoothing Constant (this applies appropriate weight to the most recent security price, using the number of periods specified in the moving average. The most common smoothing constant is 2, but the higher it is the more influence recent data points have on the EMA)

How to Calculate EMA

Technical analysts follow three steps to calculating an EMA.

1.    Calculate the simple moving average (SMA) to find the initial EMA data point. The SMA is used as the previous period’s EMA for the first calculated data point of the EMA. To calculate the SMA of the last 20 days, a trader would add the amounts of the last 20 closing prices of the security and then divide that sum by 20.

2.    Calculate the weighting multiplier for the number of periods that will be used to calculate the EMA. The number of periods used for the EMA has a significant impact on the value of the weighting multiplier.

   The formula for finding the weighting multiplier is:

   EMA(current) = ((Price(current) – EMA (prev)) x Multiplier) + EMA(prev)

3.    Calculate the EMA using the formula described above.

Some traders also use the open, high, low, or median price instead of the closing price for the EMA calculation.

What Does EMA Show You?

An EMA follows prices more closely than a SMA since it puts more weight on recent data points. This is helpful for determining when to enter and exit trades. EMA is a lagging indicator that shows market trends and directions and the strength of price movements. It’s best used in trending markets.

By looking at past trends traders can gain an understanding of what might happen with a security’s price in the future, which may help them identify investment opportunities. Although past performance is no guarantee of future performance.

Which EMA Is Best?

Day traders often use 8- and 20-day EMA periods, while long-term investors use 50- and 200-day EMA. Indicators such as the moving average convergence divergence (MACD) and percentage price oscillator (PPO) use 12- and 26-day periods. If a security passes over a 200-day EMA this is a technical sign that a trend reversal has occurred.

Limitations of Using EMA

Although EMA is a very useful trading tool, it does have some constraints.

Limitations of EMA

•   Spotting trends and directions using EMA is difficult in a flat market.

•   The EMA shows present market trends but is not a predictor of future trends and prices. It also doesn’t show exact highs and lows or precise entry and exit points.

•   The EMA can show false signals and can show more short term price changes that aren’t trading indicators.

•   Even though it is weighted toward recent prices, the EMA does rely on past price movements, so it is a lagging indicator. Because of this the optimal time to enter a trade may have already passed by the time the trend direction shows up in an EMA chart.

Difference Between EMA and SMA

Both simple moving average and exponential moving average are used by traders to measure market trends. They both create a graphical line that smoothes out price fluctuations using calculated averages.

But EMA and SMA are different in a few ways:

•   SMA calculates the average price data of a security over a given time period. EMA puts more weight on recent price data within the time period.

•   A given data point in an SMA doesn’t depend on SMA calculations from previous days. A given EMA data point depends on all previous EMA calculations. In order for an EMA to have accuracy it needs many data points.

•   An SMA is not as sensitive to price changes as an EMA, making it easier to spot trends quickly using an EMA. The SMA is a smoother line and doesn’t react as quickly to changes in asset price.

Both EMA and SMA are useful tools for traders. Day traders tend to prefer EMA since it puts weight on recent prices and reacts more quickly to changes in price than SMA.

How Investors Can Use EMA

Usually traders look at the direction the EMA is going in and they trade in the direction of the trend. In addition to spotting market trends and direction, EMA can also identify spot reversals that occur when a security is overbought or oversold.

The EMA is a fairly accurate tool because stock prices typically only stray so far from the average before returning to test the average, creating support or resistance and continuing to rise or fall. Even beginning investors can use EMA to spot trends and gain an understanding of what direction the market is heading.

Like other indicators, It’s best to use EMA in conjunction with other tools such as relative strength index (RSI) and moving average convergence divergence (MACD) to get a more comprehensive and accurate picture of the market. There are a few ways investors can use EMA:

Trend Trading

Traders can use the EMA to discover and trade primary market trends. When the EMA rises this is a bullish indicator, a trader may buy when the stock price dips to hit the EMA line or just below it. When EMA goes down, a trader might sell their position when the stock price goes up to hit the EMA line or just above. If the stock has a closing price that crosses over the average line, the trader closes out their trade.

Recommended: The Basics of Trend Trading

Support and Resistance

EMA lines can track support and resistance levels, another useful way to track price movements and trends. If EMA goes up, this is a support indicator, while if it goes down this shows resistance to the security’s price movement.

Buy and Sell Signals

Traders can set up fast and slow moving averages and then find buy and sell signals when the two lines cross each other.

The Takeaway

EMA is a useful tool for both advanced and beginner traders to understand market trends and directions. It’s a technical indicator that evaluates a stock’s price trend with a greater emphasis on recent price levels.

Whether you’re planning to use in-depth technical analysis or not, a great way to get started building a portfolio is by opening an investment account on the SoFi Invest® stock trading app. It lets you research, track, buy and sell stocks, exchange-traded funds, crypto, and other assets right from your phone.

Photo credit: iStock/South_agency

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