Simple Moving Average
An SMA adds the selected closing prices and divides by the number of observations. Every price inside the selected window has equal weight.
Exponential Moving Average
EMA applies greater weight to more recent observations, making it generally more responsive to new price changes than an SMA using the same nominal period.
Using moving averages for trend context
Price above a rising moving average can describe an upward environment; price below a falling moving average can describe a downward environment.
This is a description of historical price behavior rather than a forecast.
Moving-average crossovers
Traders sometimes compare a faster average with a slower average. A faster average crossing above a slower one indicates recent prices have strengthened relative to the longer window.
Common moving-average mistakes
Treating an average as exact support
Price can cross a moving average repeatedly.
Adding many similar averages
Multiple averages derived from the same price series may add less independent information than expected.
Ignoring lag
Both SMA and EMA summarize historical data.
How SMA and EMA weighting differs
An SMA gives each observation in its lookback window equal weight. A 20-period SMA is therefore the arithmetic mean of the most recent 20 values.
An EMA applies greater weight to more recent observations and progressively less weight to older observations. This generally makes an EMA react faster to recent price changes than an SMA using the same nominal period.
The period changes sensitivity
A shorter moving-average period usually responds more quickly to price but also changes direction more frequently. A longer period is smoother but reacts more slowly.
The appropriate period depends on the timeframe, market and purpose of the rule; there is no universally best moving-average length.
Price relative to an average is context, not proof
Price trading above a moving average can describe positive recent price context, while price below it can describe negative recent context. The meaning depends on how the average is defined and the market regime.
During sideways markets, price may repeatedly cross the same average without producing a durable trend.
They summarize historical price data. A crossover or price interaction does not guarantee that the next move will continue in the same direction.
Key takeaways
- SMA weights observations equally within its window.
- EMA gives more weight to recent observations.
- EMA generally responds faster to new price movement.
- Moving averages can help describe trend but cannot guarantee continuation.
Sources & further reading
This lesson is educational material. Market structure, exchange rules, fees, margin requirements and derivatives mechanics can differ by venue and can change over time. Verify current rules with the venue you use.