How to Change the Intervals on an X-Axis in Excel. The X-axis, which is the horizontal axis, on most Excel charts does not use numeric intervals like the vertical Y-axis does.

Use your mouse to size the graph's vertical and horizontal axis equally. Click the "Save" button to save the changes to the spreadsheet and the graph.

If you have uneven distribution of data in your Excel chart, here is a better way to change the automatic axis settings.