Nearly 46 inches tip-to-tip works for me. But I'm 5' 9" (1.75 m) tall and deal with bat'leths on a daily basis. But perhaps you aren't; perhaps you are only 5 feet (1.525 m) tall. How do we arrive at a configuration for you? No problem
Kneel down on the ground (as flat a stretch of ground as you can find). Have a buddy measure you from the top of your head to the ground. This measurement will give you the tip-to-tip length of your bat'leth. Remember to be on one knee. This measurement is devised so that in the event you take a serious wound to the leg, you can drop on one knee and continue to fight effectively.
The pIn'a' and the ghojwI':
These are the handle holes. To determine the length of them, lay your hand flat on a table and stretch your fingers out as far apart as is comfortable. Measure from the tip of your thumb to the tip of your pinkie finger across the back of your hand. This should yield the length of these "holes". These holes then are as wide at the center as your clenched fist as if punching something. (visualize your knuckles against a flat surface, and you're measuring from the middle knuckle to the bottom of your thumb under the clenched fist. i.e. Basically the height of your fist.)
This measurement is taken from the tip of your thumb to the first knuckle of the thumb ad 1/4 " (6.53 mm). This measurement also yields the distance between the "holes" mentioned above.
This is a bit trickier, but if you can do some basic math, no problem. The curvature of the bat'leth is a 3:1 ratio. Basically, for every 3 inches (7.63 cm) the bat'leth is long, it is 1 inch (2.54 cm) wide, i.e. a 45 inch (114.3 cm) bat'leth is 15 inches (38.1 cm) wide.
The tip of the van(s) are 2 inches (5.08 cm) shorter than the tip of the tiq(s).
The rest you are pretty much on your own for. I have provided a sketch with the section on the anatomy of a bat'leth that can be enlarged to yeild a pattern. Only minor modifications need be made. Remember that a bat'leth is symmetrical. You really only need a "half" of a bat'leth pattern and a good "T-square".