Level 2 · Lesson 1 / 11 · English
Simple Moving Average (SMA)
4 min reading · Exercises take additional time
0 of 11 lessons completed for this visit
A simple moving average summarises recent prices by giving every observation in a selected window equal weight. It can make a noisy chart easier to describe, but it does not reveal future prices. The related chart uses computed hypothetical data for learning, not live quotes or evidence of a profitable strategy.
What you will learn
- Calculate an SMA and explain how its rolling window changes.
- Distinguish trend description from a trade prediction.
- Recognise lag, parameter sensitivity and range-market whipsaws.
Illustrative educational chart · Not live market data
Calculation and the rolling window
For a period of n completed bars, add the selected price from each bar and divide by n. Closing prices are common, but another input produces a different series. A three-period SMA needs three observations before its first complete value. When another bar closes, remove the oldest observation, add the newest and divide by three again.
An SMA measures price in the same units as its input. On an hourly chart, a 20-period SMA represents 20 hourly observations, not 20 days. Missing bars, trading sessions and differences between data feeds can change the result. Record the timeframe, price input and treatment of incomplete bars before comparing charts.
Interpreting slope and crossings
A rising SMA indicates that the rolling average is increasing. Price above it means the current price exceeds that particular historical average; it does not mean the asset is objectively cheap or that buying is justified. A fast average crossing a slow average describes a change in their relative positions, not an independent forecast.
Moving averages often look clearer during sustained trends. In sideways conditions, price can repeatedly cross the average, generating contradictory signals and trading costs. Because every observation has equal weight, an old extreme price leaving the window can change the average even when the newest price barely changes.
Settings and responsible use
Short windows respond sooner but fluctuate more. Longer windows smooth more heavily and usually react later to reversals. Neither setting is universally best. Familiar choices such as 20, 50 or 200 periods are conventions that need evaluation against the instrument, timeframe, costs and purpose of the analysis.
If testing an SMA rule, specify whether a crossing requires a completed bar and when an order could actually execute. A decision using the closing price should not assume an earlier fill within that same bar. Define exits, position size and maximum loss separately; an average is not a guaranteed support level or protective stop.
Key terms
- SMA
- The arithmetic mean of prices in a fixed rolling window.
- Lag
- The delayed response created by using historical observations.
- Whipsaw
- Repeated reversals that can trigger losing or costly signals.
Hypothetical worked example · Not live market prices
Hypothetical three-period SMA
- Take three completed closing prices: 10, 12 and 14.
- Calculate (10 + 12 + 14) ÷ 3 = 12.
- If the next close is 16, discard 10: (12 + 14 + 16) ÷ 3 = 14.
| Window | Sum | SMA |
|---|---|---|
| 10, 12, 14 | 36 | 12 |
| 12, 14, 16 | 42 | 14 |
Simplified educational calculations. Costs, slippage and provider-specific adjustments apply where relevant; these are not actual returns.
Common mistakes to avoid
- Treating a crossing as a promise rather than a testable condition.
- Comparing different timeframes as though their periods represent equal durations.
- Selecting the best-looking window after inspecting the entire price history.
Lesson summary
An SMA is an equal-weight historical average. Its usefulness depends on market conditions, consistent settings and realistic testing, not on any fixed predictive ability.
Practical exercise
Calculate a three-period SMA for closes 8, 10, 12, 14. The two complete values are 10 and 12. Explain why the second average still sits below the latest close.
Knowledge check
Check your understanding
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Related lessons
Financial education, not personal investment advice. Leveraged Forex and CFDs can lead to substantial losses. Demo practice and correct quiz answers do not guarantee trading success.