Nine Days: Siyum
Question
If I want to make a siyum during the 9 days how many men have to be there
Answer
Shalom!
Thank you for your question.
The rules of a siyum during the Nine Days are as follows:
During the Nine Days you may invite anyone you wish to partake of the siyum seuda. There are no restrictions on the number.
Only those who would have also joined you for your siyum if it would have been held at any other time of the year are permitted to join you. (i.e. we do not want to turn a siyum in the Nine Days and an excuse to eat meat)
If the siyum is being held during “shavua shechal bo” – the week
in which Tisha B’av occurs, only your close family may join you plus an additional
10 guests.
Source
OC 551 and commentaries