Data in Different Scales

When you add multiple series, each series should use the same scale. In other words, the points for each series should be plotted (placed on the chart) using the same measurement system.

The worksheet in previous page figures works perfectly well because the different series of sales figures all use the same unit dollars. But if one series recorded sales totals in dollars and another recorded them in Euros (or even worse, recorded totally different data like the number of units sold), the chart would be inconsistent.

Excel doesn't complain if your series use different scales in fact, it has no way of noticing that anything's amiss. And if you don't notice either, you'll create a misleading chart.

Your chart may imply a comparison that isn't accurate or, if the scale is radically different, the chart can get so stretched that it starts to lose detail. If you have sales figures from $50,000 to $100,000 and units sold from 1 to 100, the scale stretches from 1 to 100,000, and the differences in sales totals or units sold are too small to show up at all.

What's the solution? Don't mix different scales. Ideally, convert values to the same scale (in this case, use the currency exchange rate to turn Euros into U.S. dollars before you create the chart). Or just create two charts, one for each data series. But if you really want to compare the changes in different types of data across the same categories, there's a way. in Section 18.6.4, "Creating Combination Charts" shows you how to build combination charts that fuse together two incompatible sets of data in a logical way.