How to Calculate a Moving Average in Excel
A moving average smooths out the noise in a series — sales, prices, web traffic — so the trend shows through. The dragged AVERAGE is easy to anchor wrong, and the first rows should be blank, not partial. Here's the one-click way that gets both right.
Last updated: August 2026
| Sales | 3-period moving avg | |
|---|---|---|
| 10, 20 | → | (blank, blank) |
| 30, 40 | → | 20, 30 |
| 50, 60 | → | 40, 50 |
Why the dragged formula slips
=AVERAGE(B2:B4) dragged down is the usual approach, but the relative range is easy to anchor wrong, so the window quietly shifts by a row. Worse, dragging it up to the top makes the first rows average a half-empty window — a number that looks real but isn't a true 3-period average. The Analysis ToolPak's Moving Average tool avoids the drag but stamps those early rows with #N/A and drops a chart you didn't ask for.
The 1-click way — Tellsheet's Moving Average
Select the data and run Moving Average. Choose the column of numbers, the number of periods to average over, and the decimal places (or −1 for none). It adds a trailing N-period average column beside your series, and the average only appears once a full window of values exists — the earlier rows stay blank, exactly how a moving average should read. Pairs with Percentage Change and Find Outliers.
Frequently asked questions
What does the window mean?
How many rows are averaged. A 3-period average of a row uses that row and the two before it.
Why are the first rows blank?
There isn't a full window yet, so they're left blank instead of showing a misleading partial average.
Can I set the decimals?
Yes — choose the decimal places, or use −1 to leave the average unrounded.
Does it touch my data?
It adds a new column beside the series; your numbers stay as they are.
Related Excel guides
Smooth a series in one click
Moving Average adds a trailing N-period average column — blank until the window fills, so it reads exactly the way an SMA should.
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