As gingersnap posted, I use ivape calculater.
Do yourself a favor, get 1 , 3 , & 5ml. syringes. 14guage blunt luerlock needles. Cost about 15usd at amazon.
Nicotine is available in pg vg or 50% mix. buy 100% pg 100mg nicotine. Much easier to dilute down to your liking. Remember nico is toxic at strong dilutions. Use nitrile gloves, vapor mask, & safety goggles. Appx cost 25usd at Home Depot.
I buy nicotine usp at wizard labs. They are usually B/O, for only a week, but they will get back to you in a prompt manner. Top drawer. Good luck.
Might be better to start at a lower nic base? And please practice all of the safety procedures that come with handling nic that is over 48%. If that gets on your unprotected skin you may become very ill. At 100mg it can kill since nic is after all a poision. Keep away from all pets and children and do it in an environment you can control.