Calculating floor joists

Hi,
In the new year I have to replace the entire floor in the front parlour of my Victorian Terraced house. The current joists that are there are 7x2.5 inches and 161 inches long.
I have tried looking online and finding the exact size of joists are difficult, can anyone recommend any help to calculate how many joists I'll need and on centre separation .

If it helps the length of the room is
161 inches and width 140 inches

Thanks