Not sure why you converted to metric. If you are the US and buying a table in feet and inches, just leave 3 feet on either side to pull out the chairs.

https://www.westelm.com/pages/ideas-and-advice/what-size-dining-table/

https://www.apartmenttherapy.com/dimensions-to-follow-proper-furniture-spacing-basics-149156

Your biggest table could be 3' 9 " X 4'9" or 45" X 57". Deduct 18" for your buffet so 45" x 39" is about the maximum dimensions of your table. It will seat 4.

West Elm and other sites showed to do it like that, it doesn’t make sense to me either. Weird

I am not brilliant in math & i am a new home owner I never cared to decorate apartments and damage furniture in the move so now i am trying to make this house a home. I was never bright in math.

Thnx though

Another sketch of my dining room

How many do you want to seat is really the 1 st step. So give us that to work with IMO in such a small space probably no buffet . Post some pics of the space too.

https://www.houzz.com/discussions/921263/what-size-dining-tables-work-well-in-a-12x12-dining-room-round-recta#n=526

Here's a lengthy discussion of the topic that might help you.

IGNORE WHAT I HAVE AS THIS IS A WORK IN PROGRESS

Thank you

If you prefer a visual in the room, use masking tape to mark out a 3 foot wide border around the room. That space needs to be there for chairs. What is left in the middle is the space for your table. If you want to keep a buffet, then mark 3 feet from the edge of the buffet.

Thank you so much ill be doing the visual for sure

Your round table looks to be a good size for the room. Maybe just work with what you have and buy chairs for it? As a new home owner you probably have lots of other things that you need to buy too.

Thank you, my table is 51 i just used my measuring tape. & yes i do