01 / Formula
Formula
SMAₜ = (Pₜ + Pₜ₋₁ + … + Pₜ₋ₙ₊₁) / n
Notation
- SMAₜ
- simple moving average at time t
- Pₜ₋ᵢ
- observed price or value i periods before time t
- n
- number of observations in the rolling window
02 / Explanation
A small numerical example
Suppose five monthly closing prices are €100, €104, €102, €108 and €111. The five-period SMA is:
(100 + 104 + 102 + 108 + 111) / 5 = 105
If the next closing price is €115, the window drops €100 and includes €115. The updated SMA becomes (104 + 102 + 108 + 111 + 115) / 5 = 108.
How the indicator is calculated
- Choose a window length that matches the frequency and purpose of the analysis.
- Take the latest n observations, including the current one.
- Add those observations and divide the total by n.
- Move the window forward by one period and repeat.
A longer window produces a smoother series but reacts more slowly. A shorter window follows recent movements more closely, while retaining more short-term variation.
Practical application
SMA is useful for describing the direction and level of a noisy time series. An analyst can compare a market price with its SMA, compare a short-window SMA with a long-window SMA, or use it as a baseline for evaluating other smoothing methods. The same calculation can summarise prices, volumes, rates or operational measurements when equal treatment of observations is appropriate.
Advantages
- The calculation is transparent and easy to reproduce.
- Every observation within the window receives the same weight.
- It provides a stable baseline for comparing more responsive moving averages.
- Its fixed window makes the underlying data scope immediately understandable.
Limitations
- Equal weighting may understate the relevance of the newest information.
- The average reacts only when values enter or leave the selected window.
- A sharp old observation can cause a visible change when it drops out.
- Window choice is subjective and does not remove uncertainty or forecast future values by itself.
Comparison with EMA and WMA
Unlike the exponential moving average, SMA does not retain a diminishing influence from observations outside a strict window. Unlike the weighted moving average, it does not assign a custom or linearly declining set of weights. SMA is therefore the simplest of the three, but usually the least responsive when they use comparable periods.