It would be better if you could share which particular exam you are asking for because the cut off varies accordingly and there are only 2 major exams of B.Arch and these are NATA and Jee main paper 2 so the cut off varies college, ctegory and homestate wise like for decent NITs your rank should come under 6k and if you talk about NATA then to get seat in top colleges more than 140 would be required.

Hope his helps!!!