Technical analysis

Moving average

Moving average is the average of a stock’s prices over a rolling number of trading periods, used to smooth short-term fluctuations and describe its past price trend.

What it means

A moving average smooths a stock’s price history by replacing each day’s price with an average calculated from a rolling window of prices. A 5-day moving average uses five trading days, not five calendar days. When a new trading day is added, the oldest day drops out.

Moving averages are technical-analysis indicators: they describe historical prices. A line rising on a chart indicates that the average of its included prices has risen, but it cannot establish what the next price will be. Common versions include the simple moving average (SMA), which gives every observation equal weight, and the exponential moving average (EMA), which gives more weight to recent observations.

The choice of price matters. An average based on closing prices can differ from one based on opening prices. Chart displays may also adjust historical prices for stock splits or dividends, changing the values shown. Comparisons are meaningful only when the price series and adjustment method are consistent.

How it is calculated

For an SMA of closing prices, use:

SMA_t(N) = (P_t + P_(t−1) + ... + P_(t−N+1)) / N

  • SMA_t(N) is the simple moving average at trading period t, in the same currency per share as the prices.
  • P_t is the closing price at period t; P_(t−1) is the previous trading period’s closing price, and so on.
  • N is the number of trading periods in the window, with no unit of currency.

You need at least N observations to calculate an N-period SMA. An EMA uses a different, recursively weighted formula, so an EMA and SMA with the same stated period will generally differ.

Worked example

Suppose a hypothetical stock closes at US$20, US$22, US$24, US$26 and US$28 over five consecutive trading days.

  1. Add the five closing prices: US$20 + US$22 + US$24 + US$26 + US$28 = US$120.
  2. Divide by five: US$120 / 5 = US$24 per share. That is the day-five 5-day SMA.
  3. Suppose the next close is US$30. Drop the oldest close, US$20, and add US$30: (US$22 + US$24 + US$26 + US$28 + US$30) / 5 = US$26 per share.

The average rose from US$24 to US$26 because the new observation was higher than the one it replaced. These hypothetical prices illustrate the arithmetic, not a likely market pattern.

Why it matters before you trade

A moving average can help put a proposed trade in historical context. For example, it lets you see whether today’s price is above or below an average of recent closing prices. A short window responds to price changes faster than a long one, but it also follows short-lived fluctuations more closely. A long window is smoother and reacts more slowly.

Neither a crossover nor a price moving above an average establishes that an order will fill at the displayed price. A moving average is calculated from past observations; an actual trade encounters current quotes, available liquidity, bid-ask spread and potentially market impact. Those execution conditions matter particularly when an order is large relative to normal trading volume.

How PreTrAIde uses it

PreTrAIde does not list a moving-average indicator among its stated quantitative measures. Its pre-trade analysis is not chart-pattern technical analysis: it assesses a proposed stock basket before an order is placed, including estimated spread, participation in daily volume, market impact, volatility and other risk and execution measures.

For each basket and stock line, PreTrAIde returns a GO, NO-GO or MODIFY verdict with reasoning. Those verdicts are decision support, not recommendations. A moving average may describe the chart a user is viewing, while a pre-trade check addresses different questions about the proposed basket and its execution conditions.

Common mistakes

  • Treating an average as a forecast. It summarizes earlier prices; it does not predict the next one.
  • Confusing trading days with calendar days. A 20-day stock-price average normally refers to 20 trading sessions.
  • Comparing unlike calculations. An SMA and EMA weight observations differently, even when both are called “20-day.”
  • Ignoring the price series. Closing-price, opening-price and differently adjusted series can produce different averages.
  • Mistaking a chart signal for an execution check. A moving average does not measure the spread, available volume or the cost of placing an order.

Frequently asked questions

How do you calculate a 20-day moving average?

For a 20-day simple moving average, add the closing prices from the latest 20 trading days and divide by 20. Repeat the calculation each trading day, dropping the oldest close and adding the newest.

What is the difference between a simple and an exponential moving average?

A simple moving average weights every price in its window equally. An exponential moving average gives greater weight to recent prices, so it generally responds faster to new observations.

Does a price crossing its moving average mean the stock will keep rising?

No. A crossing describes the relationship between a current price and an average of earlier prices; it does not establish the direction of future prices or the cost of executing a trade.

Related terms

Technical analysis Technical analysis is the study of historical prices, trading volume and chart-derived indicators to describe market trends and patterns, without relying primarily on company financial statements. Momentum Momentum is the tendency of a stock’s recent price direction to persist for a period, often measured by its return over a specified lookback window. Mean reversion Mean reversion is the tendency of a variable, such as a stock’s price or return, to move back toward a specified historical average after deviating from it. Volatility Volatility is a measure of how widely an asset’s returns vary over a specified period, usually expressed as the standard deviation of returns. Pre-trade analysis Pre-trade analysis is the assessment of a proposed stock order or basket before placement, estimating execution costs, liquidity and risk to inform the investor’s decision and execution approach. Execution cost Execution cost is the amount paid to complete a trade beyond a chosen reference price, including the effect of the fill price and, when specified, trading fees.

Technical analysis

Relative strength index (RSI) MACD Bollinger Bands Support and resistance Trend following Breakout Market sentiment analysis News trading All glossary terms →

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Educational content, not investment advice. PreTrAIde is analysis software, not a broker: it never executes orders, and its verdicts are decision support, not recommendations to buy or sell.