Excel VSTO - cm inches to point conversion not accurate

Question

I've been working on a unique ribbon bar that has the ability to resize charts to fit within a PowerPoint slide template we have.

The accepted wisdom is to utilize a standard 28.35 points to 1 cm to cm conversion function. This doesn't appear to be accurate, though.

For instance, if the input for the conversion function is 6.7 cm, the width of the chart that is embedded in PowerPoint will be 6.88 cm.

This has been tried:

• At various sizes
• Converting CM to inches and then inches to points
• Using the built-in method: https://msdn.microsoft.com/en-us/vba/excel-vba/articles/application-centimeterstopoints-method-excel

It never comes up accurately.

I have not been able to find any mention of "external factors" that may impact how it appears (such as display resolution, slide size, etc).

Any ideas why this would happen and what workaround options there are?

Answer 1

You may convert centimetres to points in Excel VBA more precisely by dividing the centimetres by 0.035278. They utilise a point-to-centimeter ratio of 28.35, which is too rounded and leads to inaccuracies. You could calculate it for inches as well by creating a macro to resize, then dividing the points number by your inches to achieve a more precise conversion calculation.