Simply in standard arabic .. غرفة means a room that's above ( 1st or 2nd floor or above ) حجرة means a room that's under the 1st flood but in dialect they are both used to describe a room , a place with 4 walls for example

by the way i must give an example more: in prisons, each room that kept inside crimers called HOJRAH, not ghorfah. i think this will give you clause to understand the difference

the differences between them that غرفة used for room which is in high place like in the 2nd floor and ect for that in quran u can find that houses in heaven called غرفة because they are in high place while حجرة room in place which arent high like in basment and ect here is the diffrences قال الراغب في الأصفهاني -في المفردات (ص/360)- : "والغُرفة: عُلِّيَّةٌ من البناء، وسمي منازل الجنة غرفا". وقال البغوي -في تفسيره (6/100)- "والغرفة: كل بناء مرتفع عال". وقال ابن عاشور -في تفسيره (19/84)- : "والغرفة: البيت المعتلي يصعد إليه بدرج وهو أعز منزلاً من البيت الأرضي". also alot of arabic native speakers cant diffrentiate between them .. so u can called room حجرة او غرفة they will understand u very well hope it useful

حجرة also means room and chamber. so what is the difference between them? i may say the difference is ghurfah used for rooms that imposed different meaining to each one to describe them, like bedroom, bathroom, living room.... as we see all of them rooms but purposes of use are different. hojrah is used for the rooms that all descibed for the same purposes. native spaekers may know better, i am not a native araic speaker. but this is my opinion

you can use the both and that will be ok