Just looked up formula and I gave you a bit excessive shorting. Looks like it should be about 95% of half wavelength for dipole length, end to end with 1.8 cm diameter rods. This is net tip to tip, including any gap you might have at feed point on boom.
For 100 MHz, that is (2.998e10 / 100MHz) X 0.5 X 0.95 = 142.4 cm. or 56 inches tip to tip.
If your dipole is attached at the center to a metal mast, the metal mast capacitance to the antenna rods will shorten it a bit more. Take off another 1% for a correction factor of 94%.
If you are going to a 50 ohm coax make sure you use a balun to balance the feed point. A 23.6 inch coax shield connected to feed point coax center conductor at the dipole center feed, taped in parallel with feed coax and grounded to feed coax shield at far end of 23.6 inch coax will act as balun. (takes unbalanced coax feed to balanced feed for dipole). It forms a parallel line of quarter wavelength.