It is actually a little worse than you think. Although, Excel supports 65,536 rows it only allows you to plot 32,000 points in a 2D data series, 4,000 in a 3D data series and 256,000 points overall.

See Excel specifications and limits for more details.

The usual workaround is to add more than one data series to a chart, each with 32,000 points, up to the limit of 256,000.

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John.