EMA vs. SMA: Exponential vs. Simple Moving Average

Search Fintrev

Search our guides, reviews and glossary.

The difference between an EMA and an SMA comes down to weighting. A simple moving average (SMA) gives every price in its window the same weight. An exponential moving average (EMA) gives the most recent prices more weight and older prices progressively less. Because of that, the EMA turns sooner when price changes direction, and the SMA moves more steadily but reacts later. Neither one is better in general. The right choice depends on how quickly you need a signal and how much noise you can tolerate.

What each moving average measures

Both indicators smooth a price series so the underlying direction is easier to see than in the raw candles. They are usually calculated on closing prices, although the formulas work on any input.

The SMA is the most familiar version and is often what charting software means by a plain “MA.” When someone refers to the “200-day moving average” without qualification, they usually mean the 200-day SMA. You may also see “DMA” (daily moving average) used in some markets, which describes the timeframe rather than the method. A 50 DMA can be simple or exponential, so check the indicator settings.

The EMA belongs to the family of weighted moving averages. Its weights decline geometrically: each older price receives a fixed fraction of the weight given to the price after it. In theory the EMA never fully forgets old data, but the influence of distant prices quickly becomes negligible. The same technique is known outside trading as simple exponential smoothing.

How to calculate the SMA

Add the last N closing prices and divide by N:

SMA = (P1 + P2 + … + PN) / N

For a 20-day SMA, you add the last 20 closes and divide by 20. If those 20 closes sum to $311, the SMA is $311 / 20 = $15.55. On the next day, the oldest close is removed, the new close is added, and the average is recalculated. Each of the 20 prices carries exactly 5% of the weight, whether it is from yesterday or from four weeks ago.

How to calculate the EMA

The EMA needs two pieces: a multiplier and a previous EMA value.

1. Multiplier: 2 / (N + 1). The 2 is the smoothing factor, and it is the standard choice. For a 20-period EMA: 2 / 21 = 0.0952.
2. Starting value: Because the formula needs a prior EMA, the first EMA is usually seeded with the SMA of the first N prices.
3. Each new period: EMA = (Close × multiplier) + (Previous EMA × (1 − multiplier))

The multiplier is the share of weight given to the newest close. Here is how it changes with the period length:

Compare the 20-period rows. A 20-day SMA gives the latest close 5% of the weight. A 20-day EMA gives it 9.52%, nearly double. Because the EMA depends on its seed and on every value since, two platforms can show slightly different EMA readings if they start the calculation at different points in the history. The gap shrinks as more data accumulates.

Worked example: the same prices, two averages

This hypothetical 5-period example uses round numbers to show the mechanics. It does not reflect any real market. The EMA multiplier is 2 / 6 = 0.3333, and the EMA is seeded with the day-5 SMA.

Three behaviors show up in this small sample:

• Faster reaction. On day 6, price jumps to 26. The EMA rises 1.60 to 22.80, while the SMA rises 1.20 to 22.40.
• Direction after the spike. On day 7, price falls back to 22. The EMA turns down at once. The SMA keeps rising to 22.60, because the day-2 close of 21 left the window and was replaced by 22. The SMA’s direction depends on what drops out as well as what comes in.
• The drop-off effect. From day 7 to day 11, price sits flat at 22. The EMA eases lower smoothly. The SMA stays elevated until day 11, then falls 0.80 in a single day. Nothing happened to price that day. The 26 from day 6 simply exited the five-day window.

That last point is the SMA’s best-known limitation. It treats a price as fully relevant until the day it disappears, and then as completely irrelevant. The EMA fades old data gradually, so it has no comparable jump.

Where the difference matters in trading

Lag and signal timing

Every moving average lags price because it is built from past data. An N-period SMA’s data points have an average age of (N − 1) / 2 periods. With the standard 2 / (N + 1) multiplier, an N-period EMA has the same average age, but its weight is concentrated on the latest bars instead of spread evenly. In practice, the EMA tracks recent moves more closely, while the SMA stays anchored to the middle of its window.

Crossovers

A common setup uses two averages: a fast one and a slow one. A buy signal comes when the fast average crosses above the slow one, and a sell signal when it crosses below. The 50/200 crossover is widely watched. A 50 crossing above the 200 is called a golden cross, and the reverse is a death cross. These levels are traditionally quoted as SMAs. Built with EMAs, the same pair crosses earlier after a turn, but also more often when the market moves sideways. If you trade on a crossover, decide in advance which type you are using, because the signal dates will differ.

Dynamic support and resistance

In trending markets, traders often watch whether price pulls back to a moving average and holds. A 20-period EMA hugs price more tightly, so pullbacks reach it more often. A 200-period SMA sits farther away and gets tested less often. These lines work alongside horizontal levels rather than replacing them. Support and resistance covers how those levels are identified.

Whipsaws

The EMA’s sensitivity is a drawback when price chops back and forth without a trend. A short EMA will flip direction repeatedly and generate crossovers that reverse within a few bars. An SMA of the same length filters more of that noise, at the cost of confirming genuine turns later.

Choosing between EMA and SMA

Match the average to your holding period. Short-term traders who need early signals often choose EMAs, and 8- and 20-period EMAs are frequent choices. On very short timeframes, such as scalping or intraday day trading, responsiveness usually matters more than smoothness. Longer-term traders and investors tend to watch 50- and 200-period averages, where a steadier line helps them avoid reacting to every pullback.

Swing trading sits in between. Swing traders often use a 20- or 21-period EMA to time entries within a trend and a 50- or 200-period SMA to define the trend itself. Using both types for different jobs is common and perfectly valid.

200 SMA vs. 200 EMA. At long lengths, the two lines usually sit fairly close together. Over a strong, extended trend, though, the gap can widen to a few dollars on a stock or many pips on a currency pair. For a trader placing stops or entries at the line, especially in large size, that gap affects fills and results. Because the 200-day SMA is the conventional benchmark, it is the level many market participants are watching.

50-day: SMA or EMA? Neither is “stronger.” The 50 EMA flags a change in trend earlier, and the 50 SMA changes direction less often. If you want the line most commonly cited in market commentary, use the SMA. If you want earlier warnings and accept more false ones, use the EMA.

Forex specifics. Currencies trade around the clock, so a “daily close” depends on the time your chart uses to end the day. Two platforms set to different server times can show different daily moving averages for the same pair. Knowing the forex trading sessions helps you understand which part of the day each candle captures.

Test before you commit. A crossover rule that works on one instrument or timeframe may fail on another. Running both averages on historical charts, or in a stock market simulator, shows how often each type would have triggered and how much later the SMA’s signals came.

Limitations of both

Moving averages describe what price has done. They do not forecast it. Both types lag, and both perform best in trending markets and worst in ranges. The EMA’s earlier signals come with more noise, and the SMA’s cleaner signals arrive later, sometimes after much of a move is over. Many traders pair a moving average with a momentum measure such as the Relative Strength Index (RSI) or with price action on candlestick charts, rather than acting on a crossover alone.

FAQs

The Bottom Line

Traders who use moving averages to time entries, set stops or read trends need to know which type their chart shows, because the EMA and SMA give different signal dates. Short-term traders often favor the EMA for earlier warnings despite more false signals, while longer-term traders lean on the steadier SMA, especially the widely watched 200-day line. Testing both on historical charts before committing shows how each behaves on a given instrument.