This is written in reference to How to Scale text in different Scripts.
If the title seems confusing, what I meant is how a sentence in Samskritham is often more phonetically complex than a sentence in English, and so representing the sentence is difficult in the limited Roman script, and while you are able to represent them in Roman script with diacritics and the Devanaagari script, the Devanaagari script seems more condensed than the Roman script with diacritics. But then, if you scale up Devanaagari text to match the Roman script with diacritics (in terms of length) for a given statement, the same scale applies to all other sentences.
Basically, different scripts have different number of graphemes, and they can represent a different number of phonemes. It should seem like there is no correlation. But when you make it so that you can fairly easily represent each phonogram using another script, the length of phonograms will turn out to be similar due to information density.
That is, while the natural English language does not have as varied of a phonemic vocabulary and the corresponding Roman script does not have as varied of a graphemic vocabulary to support non-English sounds, with diacritics, new sounds and letters are generated. After that, it is only necessary to align the letters to equivalent sizes.
Now, why I emphasized phonograms was because if you only used graphemes, then you could go about doing this using the standard Roman script without any diacritics, but then representing different sounds would become difficult, and so the scaling would never work out right. For example, one would need “aa” for an elongated “a” and so on, leading to length mismatch between phonograms.