Field Guide to Trading Terms

Exponential moving average

Family VI · Charts & indicators

Not to be confused with simple moving average, average true range, moving average, moving average crossover.

Exponential moving average (EMA) is a type of moving average that applies a weighting factor to each price in a series, with the most recent prices receiving the highest weight. This design makes the EMA more responsive to recent price changes than a simple moving average of the same period. Traders use EMAs to smooth price data and identify trends, often in crossover strategies.

Calculation

The EMA is computed recursively. First, an initial EMA value is set, often as the simple moving average of the first n prices. Then, for each subsequent price, the EMA is updated using the formula:

EMAtoday = (Pricetoday × k) + (EMAyesterday × (1 − k))

where k is the smoothing constant, typically calculated as k = 2 / (n + 1) and n is the chosen period. The value of k determines the weight given to the most recent price; a higher k (shorter period) makes the EMA more sensitive.

Worked example

Assume an EMA period of 5 days, so k = 2 / (5 + 1) = 0.3333. The initial EMA (day 1) is set to the closing price of 100.00. The subsequent closing prices and EMA calculations are shown below.

EMA calculation for a 5-day period
Day 1 close100.00EMA = 100.00
Day 2 close102.00EMA = (102.00 × 0.3333) + (100.00 × 0.6667) = 100.67
Day 3 close101.00EMA = (101.00 × 0.3333) + (100.67 × 0.6667) = 100.78
Day 4 close103.00EMA = (103.00 × 0.3333) + (100.78 × 0.6667) = 101.52
Day 5 close104.00EMA = (104.00 × 0.3333) + (101.52 × 0.6667) = 102.35

The final EMA value of 102.35 reflects the most recent price more heavily than a simple moving average would.

Interpretation and use

The EMA is used to identify the direction of a trend and potential support or resistance levels. Because it reacts faster to recent price changes, it can generate signals earlier than a simple moving average, but it may also produce more false signals in choppy markets. Common applications include using a single EMA to gauge trend direction, or multiple EMAs of different periods to generate crossover signals.

Often confused with

simple moving average
A simple moving average gives equal weight to all prices in the period, whereas an exponential moving average weights recent prices more heavily; the visible sign is that the EMA line turns more sharply than the SMA line after a sudden price change.
average true range
Average true range measures market volatility by averaging true range values, while an exponential moving average smooths price data to indicate trend direction; the visible sign is that ATR is plotted as a separate line below the price chart, whereas an EMA is overlaid on the price chart.
moving average
A moving average is the broad category of indicators that smooth price data, and an exponential moving average is a specific type within that category; the visible sign is that the term 'moving average' alone does not specify the weighting method, while 'exponential moving average' explicitly indicates exponential weighting.
moving average crossover
A moving-average crossover is a trading signal generated when two moving averages intersect, whereas an exponential moving average is a single indicator line; the visible sign is that a crossover involves two lines crossing on the chart, while an EMA is just one line.

See also

Family: VI · Charts & indicators · Index A–Z