The area taken up by the type when it's live is different from the area after you outline because of the geometry of the type. For example, the word FLOWERING, when typed in all caps doesn't have any descenders like you would have with a lower-case j or p, and if you had lower-case words like aim, they wouldn't work the same as words with ascenders like Tame, or something with both, like Jimmy.
I don't know if there is a way to make this work without eyeballing it, but you can fit a text frame to the text within. The problem is that descenders will stick out of the bottom of the frame, so using distribution of the frame won't do exactly what you are after. It might work, depending on the scope of what you have to work with, but I think you will end up doing some manual tweaking in the end.
This is just a quickie example I made, but you can see that the frames (which I fit to the text in all of the examples) have their descenders sticking out, and if I distribute with no space between frames, some bits look OK and others don't.
I suppose you could make a copy of the text (maybe on another layer), outline it, and use that as a guide to move the live type, then hide or delete the outlined layer. And if you are considering outlining just for alignment, you will lose much more control of your type than you will gain in ease of alignment, at least in my opinion. Outlined type is a bad idea except for rare circumstances, and only then for small bits of type that you want to style in a particular way.
HOw did you do that? My text boxes are coming as either text in the middle or in the bottom. How did you do pefect thing? what do you mean by eyeballing. Please give a step by step procedure.
Check your Text Frame Options
Object>Text Frame Options
With no objects selected it will be the default for all new objects.
With an object selected it's the object setting.
You can change where text sits in a text frame by adjusting the Baseline options.
what do you mean by eyeballing.
If you use the alignment tools to align two text frames, the frames might be the exact distance you want, but you have to look at them with your eyeballs to know if the text within is the correct distance. You can sometimes get a better view if you go into Preview mode (View>Screen Mode>Preview, or use the W key to toggle between Preview and Normal).
To set the size of the frame to fit the content, select the frame and go to Object>Fitting>Fit Frame to Content, or use the shortcut Command Option C. You can also double-click on the edge of a frame to collapse that side of the frame to fit the content. By that I mean that if you start with this:
…and double-click the handle circled in red, it will collapse the left side to this:
…and if you double-click the handle circled in red, it will collapse the bottom to this:
You could also have double-clicked the handles on the top or right or a corner, and the only difference is the part of the frame that stays in position after the collapse.
Geometrically, type doesn't have an exact height. What attribute of the letters would you like to be 15mm deep? Your screenshot suggests the cap height. But with a 15mm cap height, letters like O will still measure over 15mm deep geometrically, as they extend beyond the cap height for optical reasons (with the exception of super-geometric square fonts). Furthermore, if you do find the point size that renders a 15mm cap height for your specific font (it will be different for different fonts), it won't fit in a 15mm deep text box.
Line spacing can be set to a specific height in mm, though, and aligning text the bottom of the text box may help, as may a Baseline Grid.
Go the "Baseline Options" tab in the middle.
Change the First Baseline
First baseline offset options
To change the first baseline options of a selected text frame, choose Object > Text Frame Options, and click the Baseline Options tab. The following options appear in the Offset menu under First Baseline:
The height of the “d” character in the font falls below the top inset of the text frame.
The top of uppercase letters touch the top inset of the text frame.
Use the text’s leading value as the distance between the baseline of the first line of text and the top inset of the frame.
The height of the “x” character in the font falls below the top inset of the frame.
Specify the distance between the baseline of the first line of text and the top inset of the frame.
Select a minimum value for the baseline offset. For example, if Leading is selected and you specify a minimum value of 1p, InDesign uses the leading value only when it’s greater than 1 pica.
If you want to snap the top of the text frame to a grid, choose either Leading or Fixed so that you can control the location of the first baseline of text in text frames.