how do i increase bar size without the bars overlapping?
Height Percentage and Fixed Bar Height do not adjust the space between bars and so all the bars overlap when they are increased in size.
Comments

You're using the horizontal bar chart?
Height percent corresponds to the amount of space each bar will take up compared to the amount of space it could potentiall fill, given an equal breakdown of space for each series bar.
At 40 height percentage
At 90:
Over 100% and the bars start to overlap.
Using the Fixed Bar Height configuration, the number you insert should be the number of pixels the bars are tall. 10 pixels, for example, being 20% of the height of a 50 pixel bar. I personally haven't really seen a use for Fixed Bar Height yet, as Height Percentage is more responsive. if you have a number in both spots, Fixed Bar Height will override whatever percentage you have entered.
Allow Tall Bars allows the bar width to exceed the typical space allotted to the graph. You probably don't need this setting unless you have your bars set using Fixed Bar Height and they are very wide (like 100+ pixels)
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Not exactly, even under 100% no matter what height above 14 pixels the bars overlap. I have elected not to use this type of graph because i can not control bar height.
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