Moving averages explained: SMA vs EMA and how traders use them
A moving average smooths price into one line so the trend is easier to see. Learn the difference between SMA and EMA, and what these lines cannot tell you.
Key takeaways
- A moving average is the average of the last N closing prices, redrawn every day.
- An EMA gives more weight to recent prices, so it reacts faster than an SMA.
- Price above a long average is read as an uptrend; a crossover of two averages is a common rule.
- Every moving average lags, and in sideways markets crossovers give many false starts.
What a moving average is
A moving average takes the average of the last N closing prices and moves forward one day at a time. The result is a smooth line that hides the daily noise. A 50-day moving average, for example, is the average of the last 50 closes.
SMA and EMA
A simple moving average (SMA) gives every day in the window the same weight. An exponential moving average (EMA) gives more weight to recent days, so it turns sooner when price changes direction. The price of that speed is more false alarms.
Common lengths
Traders often look at 20 days for the short term, 50 days for the medium term and 200 days for the long term. There is no perfect length. A shorter average follows price closely and signals often; a longer one is slower and signals rarely.
Two ways they are used
First, as a trend check: price above its 200-day average is often read as an uptrend, and many rules only act in that case. Second, as a crossover: when a faster average crosses above a slower one, momentum may be turning up. SmartPaperDesk includes EMA Crossover Momentum, which uses the 20-day EMA crossing above the 50-day EMA, and Golden Cross, which uses the 50-day average crossing above the 200-day.
What they cannot do
A moving average is built from past prices, so it always lags. It says nothing about value. In a sideways market price keeps crossing back and forth over the line, and every cross is a false start.
Test a moving-average rule on paper
Choose the two lengths, write the entry and exit, then test on historical daily data with estimated charges and a stop. Compare the number of trades and the worst dip. The free plan lets you do this with no real money.
Questions people ask
Which is better, SMA or EMA?
Neither is better. An EMA reacts faster and gives more signals; an SMA is smoother. The right choice depends on the rule and must be tested.
What moving-average length should I use?
There is no correct length. 20, 50 and 200 days are common starting points, but the result depends on the stock, the period and the costs, so test the choice.
Test a moving-average rule on the free plan
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SmartPaperDesk is an educational paper-trading tool. Examples use a made-up Stock A.
For educational purposes only. This is not investment advice. Past performance does not guarantee future results.