PPT97: PowerPoint Centimeters Different from Actual Centimeters

Microsoft PowerPoint uses an invisible grid. The grid's conversion ratio from inches to centimeters is: This is different from the accepted standard conversion ratio from inches to centimeters, which is:

Because the ruler in PowerPoint is based on the grid, the ruler uses the same conversion ratio.

In PowerPoint, the grid is based on units of one pica (1/12 inch). Because all slides have this fixed grid, you can copy objects from one slide to another, and they will accurately retain their position on the slide.

To make the benefits of a fixed grid universal, PowerPoint needs to use the same grid spacing for metric systems that is used for English systems. Since there are 4.724 picas per centimeter using the standard conversion, that means that the grid spacing falls at rather odd points on the metric scale. No round number of centimeters actually falls on a gridline. Therefore, it would be impossible to use the snap-to-grid feature to draw objects that are an even number of centimeters.

To improve its usability, PowerPoint slightly misdefines the size of a centimeter to make the invisible gridlines fall at convenient points on the ruler. With this conversion, there are 5 picas per centimeter and the gridlines fall at very convenient points on the ruler. So convenient, in fact, that working in the metric system is really easier than working in the English system. The table below shows how much simpler the metric grid is in "PowerPoint centimeters" than in actual centimeters. The only problem with this slight misdefinition of size is that the actual measurements you are making are off by six percent. Many printer drivers can be set to reduce or enlarge while printing. If your printer driver supports this, you can set the print scaling of your presentation to 106 percent to get an accurate size. The printed image will then measure precisely the way the screen does.

In PowerPoint 97, you can correct the size of the object by following these steps:

1. Select the object that needs to be a specific size.
2. On the Format menu, click AutoShape, Object, or Picture (whichever applies).
3. Click the Size tab.
4. Manually enter the correct size.
5. Click OK.