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Unlike chess, the dimensions of the backgammon points (triangles) is related to the size of the pieces.
Before marking out the points, you need to know the exact diameter of the pieces you intend using, because this will determine the width of the base line. There will be six points on each line. Therefore each base will be six times the diameter of the piece. When the base line is full of pieces side by side they should all be a snug, (but not too tight) fit inside the frame edge to edge to the bar.
The height of the points is usually equivalent to five times the diameter of a piece. You need enough space between the points to roll the dice, and allow a bar down the centre wide enough to accomodate pieces as they are borne off, plus the doublng dice.
This is due to the fast action of play.
Backgammon, played competetively, is a rapid game where each player moves as the other is throwing the dice. Pieces are slid along the board and sit alongside its neighbour on the base line - this means that they all need to line up without any displacement into the adjacent slot, which may be your opponent's point.
What I'm suggesting is that you select your set of pieces first, which will usually come with a set of die and a doubling dice, then measure the size of the board from a full base line of six, otherwise you may have fit problems which may come out in play.
Hope it helps
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