Well, these days, things are normally drawn 1:1… Drawing to scale was invented so that things larger than a sheet of paper could be fit on that sheet and represented proportionally accurately. CAD has no such sheet size limitation.
That said, if you are in possession of a scaled drawing, unless you know the approximate size of a given feature in the drawing, it’s anybody’s guess.
English and metric have different scaling conventions. English unit progressions are generally fractional often with x inches = y feet, that usually go by double or half - 1/4, 1/8, 1/16, etc. Metric scales are most often represented as 1:X and go by decimals i.e. 1:100, 1:200, 1:500, 1:1000 etc.