You got to leave a little lee-way in there to accommodate for reader perception. And oftentimes it's better to not put things up to specefics, as explained by Vilage. Metaphor and simile can go a long way to building not only a physical description but also something of an emotional description that might be experienced by others. There's a difference in weight between saying "His hair was brown" and "His hair was a rich earthen brown".

Same would apply to the sort of descriptive vehicles the federal and state government would like to have for stuff like driver's licenses. Except giving precise increments detracts all creative abstraction. You can say it for sure: but the context then becomes important. If two characters who are detectives are discussing the physical profile of someone, or there's a missing person's report on them then it would be expected that height and weight are mentioned as simply part of the dialog or on the props for that scene. But no one casually describing another person would use exact height-weight ratios, and neither should it come up in informal writing such as RP'ing or entertainment writing.

This falls into such work being classified as informal writing, where reports where specifics such as this would be deemed formal. Both fields have their mechanical expectations which would have to be met. Informal writing is to entertain so does away with a lot of dry statistics and specefics in the same way formal writing does away with metaphor and simile in order to carry information in a precise manner. Formal writing is written to be interpreted clearly with no mistake on what's being said, what the content is about, and so on. But informal story-writing is written informally like the writer is telling the reader this story person-to-person: and for that you don't use specifics.

You want to captivate the reader. Not dry them up and kill their interest with a sledgehammer of textbook profiling to the face. It needs to flow in a captivating way, with emotion as the vehicle on which it sails. So giving up height-weight ratios there's a thousand ways to describe someone as "short" or "tall". "Imposing and giant" might be a simplified way to describe a body builder, for instance.